BC30560: 'WebScriptManager' is ambiguous in the namespace 'Infragistics.Web.UI'.

1. The only Infragistics DLL in my or the server's bin is the 12.2 version.

2. Here's the web.config section with the references:

3. Here's what is at the top of my Site.Master page:

<%@ Register Assembly="Infragistics4.Web.v12.2, Version=12.2.20122.1007, Culture=neutral, PublicKeyToken=7dd5c3163f2cd0cb" Namespace="Infragistics.Web.UI.ListControls" TagPrefix="ig" %>

<%@ Register Assembly="Infragistics4.Web.v12.2, Version=12.2.20122.1007, Culture=neutral, PublicKeyToken=7dd5c3163f2cd0cb" Namespace="Infragistics.Web.UI.LayoutControls" TagPrefix="ig" %>

The detailed compile looks like this:

c:\windows\system32\inetsrv> "C:\Windows\Microsoft.NET\Framework64\v4.0.30319\vbc.exe" /t:library /utf8output /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Configuration\v4.0_4.0.0.0__b03f5f7f11d50a3a\System.Configuration.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System\v4.0_4.0.0.0__b77a5c561934e089\System.dll" /R:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\assembly\dl3\14e3493f\00987ead_e586cd01\DotNetOpenAuth.OAuth.Consumer.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\Microsoft.CSharp\v4.0_4.0.0.0__b03f5f7f11d50a3a\Microsoft.CSharp.dll" /R:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\assembly\dl3\a32a663d\8020f0a6_e586cd01\Microsoft.ScriptManager.MSAjax.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Xml\v4.0_4.0.0.0__b77a5c561934e089\System.Xml.dll" /R:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\assembly\dl3\13d8778c\80f3bea5_e586cd01\System.Web.Providers.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_64\System.EnterpriseServices\v4.0_4.0.0.0__b03f5f7f11d50a3a\System.EnterpriseServices.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\Infragistics4.WebUI.Documents.Reports.v12.2\v4.0_12.2.20122.1007__7dd5c3163f2cd0cb\Infragistics4.WebUI.Documents.Reports.v12.2.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\Infragistics45.Web.v12.2\v4.0_12.2.20122.1007__7dd5c3163f2cd0cb\Infragistics45.Web.v12.2.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Data.DataSetExtensions\v4.0_4.0.0.0__b77a5c561934e089\System.Data.DataSetExtensions.dll" /R:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\assembly\dl3\5e7c0e06\008a57a6_e586cd01\System.Web.Optimization.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.ComponentModel.DataAnnotations\v4.0_4.0.0.0__31bf3856ad364e35\System.ComponentModel.DataAnnotations.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_64\System.Data\v4.0_4.0.0.0__b77a5c561934e089\System.Data.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\Infragistics45.WebUI.Documents.Excel.v12.2\v4.0_12.2.20122.1007__7dd5c3163f2cd0cb\Infragistics45.WebUI.Documents.Excel.v12.2.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.WorkflowServices\v4.0_4.0.0.0__31bf3856ad364e35\System.WorkflowServices.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\Infragistics45.WebUI.Documents.Word.v12.2\v4.0_12.2.20122.1007__7dd5c3163f2cd0cb\Infragistics45.WebUI.Documents.Word.v12.2.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Web.Entity\v4.0_4.0.0.0__b77a5c561934e089\System.Web.Entity.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\Infragistics4.WebUI.Documents.Excel.v12.2\v4.0_12.2.20122.1007__7dd5c3163f2cd0cb\Infragistics4.WebUI.Documents.Excel.v12.2.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Core\v4.0_4.0.0.0__b77a5c561934e089\System.Core.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Web.DynamicData\v4.0_4.0.0.0__31bf3856ad364e35\System.Web.DynamicData.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_64\System.Web\v4.0_4.0.0.0__b03f5f7f11d50a3a\System.Web.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Drawing\v4.0_4.0.0.0__b03f5f7f11d50a3a\System.Drawing.dll" /R:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\assembly\dl3\3f73673b\008a57a6_e586cd01\AspNet.ScriptManager.jQuery.UI.Combined.dll" /R:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\assembly\dl3\f64c35d8\8001e6ac_e586cd01\DotNetOpenAuth.Core.dll" /R:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\assembly\dl3\c9fbd719\80f3bea5_e586cd01\Antlr3.Runtime.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.ServiceModel.Activation\v4.0_4.0.0.0__31bf3856ad364e35\System.ServiceModel.Activation.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.ServiceModel.Activities\v4.0_4.0.0.0__31bf3856ad364e35\System.ServiceModel.Activities.dll" /R:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\App_global.asax.8b2k--5e.dll" /R:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\assembly\dl3\85a098b7\8020f0a6_e586cd01\Microsoft.ScriptManager.WebForms.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.IdentityModel\v4.0_4.0.0.0__b77a5c561934e089\System.IdentityModel.dll" /R:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\assembly\dl3\a6e49b4b\00987ead_e586cd01\DotNetOpenAuth.AspNet.dll" /R:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\assembly\dl3\6d95e1fd\8001e6ac_e586cd01\DotNetOpenAuth.OAuth.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\Infragistics4.WebUI.Documents.IO.v12.2\v4.0_12.2.20122.1007__7dd5c3163f2cd0cb\Infragistics4.WebUI.Documents.IO.v12.2.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\Infragistics45.WebUI.Documents.Reports.v12.2\v4.0_12.2.20122.1007__7dd5c3163f2cd0cb\Infragistics45.WebUI.Documents.Reports.v12.2.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\Infragistics4.WebUI.Documents.Core.v12.2\v4.0_12.2.20122.1007__7dd5c3163f2cd0cb\Infragistics4.WebUI.Documents.Core.v12.2.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\Infragistics4.WebUI.Documents.Word.v12.2\v4.0_12.2.20122.1007__7dd5c3163f2cd0cb\Infragistics4.WebUI.Documents.Word.v12.2.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Activities\v4.0_4.0.0.0__31bf3856ad364e35\System.Activities.dll" /R:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\assembly\dl3\d4178a80\00c5afae_e586cd01\Microsoft.AspNet.Membership.OpenAuth.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Xml.Linq\v4.0_4.0.0.0__b77a5c561934e089\System.Xml.Linq.dll" /R:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\assembly\dl3\b995934b\008a57a6_e586cd01\AspNet.ScriptManager.jQuery.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Web.Services\v4.0_4.0.0.0__b03f5f7f11d50a3a\System.Web.Services.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Web.ApplicationServices\v4.0_4.0.0.0__31bf3856ad364e35\System.Web.ApplicationServices.dll" /R:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\assembly\dl3\aa6b5db7\96c9c956_eebdcd01\ITS.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Design\v4.0_4.0.0.0__b03f5f7f11d50a3a\System.Design.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Web.Extensions\v4.0_4.0.0.0__31bf3856ad364e35\System.Web.Extensions.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\Infragistics45.WebUI.Documents.IO.v12.2\v4.0_12.2.20122.1007__7dd5c3163f2cd0cb\Infragistics45.WebUI.Documents.IO.v12.2.dll" /R:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\assembly\dl3\505ef7dd\00987ead_e586cd01\DotNetOpenAuth.OpenId.RelyingParty.dll" /R:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\assembly\dl3\bace8d7c\00987ead_e586cd01\DotNetOpenAuth.OpenId.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.ServiceModel\v4.0_4.0.0.0__b77a5c561934e089\System.ServiceModel.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Runtime.Serialization\v4.0_4.0.0.0__b77a5c561934e089\System.Runtime.Serialization.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\Infragistics4.Web.v12.2\v4.0_12.2.20122.1007__7dd5c3163f2cd0cb\Infragistics4.Web.v12.2.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.ServiceModel.Web\v4.0_4.0.0.0__31bf3856ad364e35\System.ServiceModel.Web.dll" /R:"C:\Windows\Microsoft.Net\assembly\GAC_MSIL\System.Windows.Forms\v4.0_4.0.0.0__b77a5c561934e089\System.Windows.Forms.dll" /R:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\assembly\dl3\96408140\80f3bea5_e586cd01\WebGrease.dll" /R:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\assembly\dl3\6654c881\00b788a7_e586cd01\Microsoft.Web.Infrastructure.dll" /R:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\assembly\dl3\b0b05ffa\802e17ae_e586cd01\EntityFramework.dll" /R:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\assembly\dl3\fbcda224\00e95f97_9c7ccd01\Microsoft.AspNet.Web.Optimization.WebForms.dll" /out:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\App_Web_nwxuitma.dll" /D:DEBUG=1 /debug+ /win32resource:"C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\nwxuitma.res" /nowarn:41008,40000,40008 /define:_MYTYPE=\"Web\" /imports:Microsoft.VisualBasic,System,System.Collections,System.Collections.Generic,System.Collections.Specialized,System.ComponentModel.DataAnnotations,System.Configuration,System.Linq,System.Text,System.Text.RegularExpressions,System.Web,System.Web.Caching,System.Web.DynamicData,System.Web.SessionState,System.Web.Security,System.Web.Profile,System.Web.UI,System.Web.UI.WebControls,System.Web.UI.WebControls.WebParts,System.Web.UI.HtmlControls,System.Xml.Linq,System.Web.Optimization /warnaserror- /optionInfer+ "C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\App_Web_nwxuitma.0.vb" "C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\App_Web_nwxuitma.1.vb"

Microsoft (R) Visual Basic Compiler version 11.0.50709.17929
Copyright (c) Microsoft Corporation. All rights reserved.

C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\App_Web_nwxuitma.0.vb(787) : error BC30560: 'WebScriptManager' is ambiguous in the namespace 'Infragistics.Web.UI'.

        Private Function __BuildControlWebScriptManager1() As Global.Infragistics.Web.UI.WebScriptManager
                                                              ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\App_Web_nwxuitma.0.vb(788) : error BC30560: 'WebScriptManager' is ambiguous in the namespace 'Infragistics.Web.UI'.

            Dim __ctrl As Global.Infragistics.Web.UI.WebScriptManager
                          ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Temporary ASP.NET Files\root\e22c2559\92c7e946\App_Web_nwxuitma.0.vb(1265) : error BC30560: 'WebScriptManager' is ambiguous in the namespace 'Infragistics.Web.UI'.

            Dim __ctrl2 As Global.Infragistics.Web.UI.WebScriptManager
                           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
C:\inetpub\wwwroot\Site.Master(26) : error BC30560: 'WebScriptManager' is ambiguous in the namespace 'Infragistics.Web.UI'.

            __ctrl = New Global.Infragistics.Web.UI.WebScriptManager()
                         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~