I recently revisited an old project to add new functionality and went ahead to update the IG controls versions. When I rebuild the project I had to fix some references. However i'm having fits with one last thing. I'm getting a complation error in my XAML where I am creating a ribbon group in a ribbon tab item. The specific error is: Cannot add content to object of type 'Infragistics.Windows.Ribbon.RibbonTabItem'

The code looks like this:

<UserControl xmlns:igRibbon="http://infragistics.com/Ribbon"
             x:Class="CriticalPath.CoursewareManager.ApplicationRibbon"
             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
             xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
             xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
             mc:Ignorable="d">
  <Grid x:Name="LayoutRoot">
    <igRibbon:XamRibbon Theme="Office2k7Black">
      <igRibbon:XamRibbon.Tabs>
        <igRibbon:RibbonTabItem Header="Course">
          <igRibbon:RibbonGroup Caption="RibbonGroup" />
        </igRibbon:RibbonTabItem>
      </igRibbon:XamRibbon.Tabs>
    </igRibbon:XamRibbon>
  </Grid>
</UserControl>

I've tried using the designer to create the ribbon and it still gives me the error. There are no IntelliSense errors giving me indications of what's wrong. What's confusing me is I created a brand new WPF project and was able to get this working with no problem. Any ideas as to what could be the issue here or where I should be looking?