This was working with 10.1and I updated to the service release. And i get that error.  Nothing has changed on the xaml between the update.  Here is the control that VS points to having the issue:

<igEditors:XamTextEditor Grid.Row="2" Grid.Column="1" Grid.ColumnSpan="3" Theme="[current]" Name="xamTextEditorDescription"
                                         TextWrapping="Wrap" MinHeight="50" MaxHeight="50" VerticalScrollBarVisibility="Auto" HorizontalScrollBarVisibility="Auto"
                                         Value="{Binding Path=Description}">
                    <igEditors:XamTextEditor.Resources>
                        <Style TargetType="{x:Type TextBox}">
                            <Setter Property="AcceptsReturn" Value="True"/>
                        </Style>
                    </igEditors:XamTextEditor.Resources>
</igEditors:XamTextEditor>

I tried deleting the above control but exception still gets thrown.

The xaml is very complicated with multiple controls.

Any help will be much appreciated thank you.

Here is the error in it's entirety:
System.Windows.Markup.XamlParseException occurred
  Message='Provide value on 'System.Windows.Markup.StaticExtension' threw an exception.' Line number '82' and line position '34'.
  Source=PresentationFramework
  LineNumber=82
  LinePosition=34
  StackTrace:
       at System.Windows.Markup.XamlReader.RewrapException(Exception e, IXamlLineInfo lineInfo, Uri baseUri)
       at System.Windows.Markup.WpfXamlLoader.Load(XamlReader xamlReader, IXamlObjectWriterFactory writerFactory, Boolean skipJournaledProperties, Object rootObject, XamlObjectWriterSettings settings, Uri baseUri)
       at System.Windows.Markup.WpfXamlLoader.LoadBaml(XamlReader xamlReader, Boolean skipJournaledProperties, Object rootObject, XamlAccessLevel accessLevel, Uri baseUri)
       at System.Windows.Markup.XamlReader.LoadBaml(Stream stream, ParserContext parserContext, Object parent, Boolean closeStream)
       at System.Windows.Application.LoadComponent(Object component, Uri resourceLocator)
       at DCS.Contract.UserControls.ucContractEntry.InitializeComponent() in c:\Users\rmaldonado\Documents\Visual Studio 2008\Projects\DCS\Contract\Contract\UserControls\ucContractEntry.xaml:line 1
       at DCS.Contract.UserControls.ucContractEntry..ctor(Contract contract) in C:\Users\rmaldonado\Documents\Visual Studio 2008\Projects\DCS\Contract\Contract\UserControls\ucContractEntry.xaml.cs:line 208
  InnerException: System.Reflection.TargetInvocationException
       Message=Exception has been thrown by the target of an invocation.
       Source=mscorlib
       StackTrace:
            at System.RuntimeMethodHandle._InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeType typeOwner)
            at System.RuntimeMethodHandle.InvokeMethodFast(IRuntimeMethodInfo method, Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeType typeOwner)
            at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks)
            at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
            at System.Reflection.RuntimePropertyInfo.GetValue(Object obj, BindingFlags invokeAttr, Binder binder, Object[] index, CultureInfo culture)
            at System.Reflection.RuntimePropertyInfo.GetValue(Object obj, Object[] index)
            at System.Windows.Markup.StaticExtension.GetFieldOrPropertyValue(Type type, String name, Object& value)
            at System.Windows.Markup.StaticExtension.ProvideValue(IServiceProvider serviceProvider)
            at MS.Internal.Xaml.Runtime.ClrObjectRuntime.CallProvideValue(MarkupExtension me, IServiceProvider serviceProvider)
       InnerException: System.TypeLoadException
            Message=GenericArguments[0], 'Infragistics.Windows.Themes.Wind.Editors+Locator', on 'Infragistics.Windows.Themes.EditorsResourceSet`1[T]' violates the constraint of type parameter 'T'.
            Source=Contract
            TypeName=""
            StackTrace:
                 at DCS.Contract.App.get_XamTextEditorCurrentStyle()
            InnerException: