Yes agreed.  Even in the application, it only happens given a specific set of steps.  There is no threading going on in this instance.  I am still trying to produce the error in a separate project.  Spent a good portion of the day doing that, but still nothing. 

Based on the stack trace and the error message, this doesn't make a lot of sense. The exception seems to be indicating that there is no UIElement for the cell. But the stack trace shows pretty clearly that the user is clicking on a dropdown button in that cell - which means it must be displayed on the screen and therefore must have a UIElement.

My first guess would be that your application is using threading and something is getting out of synch.

If that's not the case, then it could be a bug, but without being able to reproduce the exception, there's no much we can do to track it down.

I am still working on producing a small project.  I'm having a difficult time reproducing outside of our application.

Apologies, I just realized I posted the call stack.  Here is the stack trace:

at Infragistics.Win.EmbeddableEditorBase.EnterEditMode(EmbeddableUIElementBase embeddableElement)
at Infragistics.Win.UltraDataGridView.UltraEditorButtonColumnBase.PrepareForEdit(Boolean selectAll, UltraDataGridViewCell cell)
at Infragistics.Win.UltraDataGridView.UltraDataGridViewCell.System.Windows.Forms.IDataGridViewEditingCell.PrepareEditingCellForEdit(Boolean selectAll)
at System.Windows.Forms.DataGridView.BeginEditInternal(Boolean selectAll)
at System.Windows.Forms.DataGridView.SetCurrentCellAddressCore(Int32 columnIndex, Int32 rowIndex, Boolean setAnchorCellAddress, Boolean validateCurrentCell, Boolean throughMouseClick)
at System.Windows.Forms.DataGridView.OnCellMouseDown(HitTestInfo hti, Boolean isShiftDown, Boolean isControlDown)
at System.Windows.Forms.DataGridView.OnCellMouseDown(DataGridViewCellMouseEventArgs e)
at System.Windows.Forms.DataGridView.OnMouseDown(MouseEventArgs e)
at System.Windows.Forms.Control.WmMouseDown(Message& m, MouseButtons button, Int32 clicks)
at System.Windows.Forms.Control.WndProc(Message& m)
at System.Windows.Forms.DataGridView.WndProc(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)
at System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)
at System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)
at System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)
at System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)
at System.Windows.Forms.Application.Run(ApplicationContext context)
at PASport.Common.Program.Main(String[] args) in C:\dotnet\PASportDev 1.x.x\PASport\Common\Program.cs:line 209
at System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)
at System.AppDomain.nExecuteAssembly(Assembly assembly, String[] args)
at System.Runtime.Hosting.ManifestRunner.Run(Boolean checkAptModel)
at System.Runtime.Hosting.ManifestRunner.ExecuteAsAssembly()
at System.Runtime.Hosting.ApplicationActivator.CreateInstance(ActivationContext activationContext, String[] activationCustomData)
at System.Runtime.Hosting.ApplicationActivator.CreateInstance(ActivationContext activationContext)
at System.Activator.CreateInstance(ActivationContext activationContext)
at Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssemblyDebugInZone()
at System.Threading.ThreadHelper.ThreadStart_Context(Object state)
at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)
at System.Threading.ThreadHelper.ThreadStart()

Hello,

I can only see the DataGridView being mentioned here. Can you provide the small sample project?