Visual-studio – Visual studio has encountered an exception

So, I'm using Visual Studio 2010, and in the past week or I'm getting a message from Visual Studio coming up: "Visual Studio has encountered an exception. This may be caused by an extension."

My ActivityLog.xml reveals logs this as the problem:

<entry>
    <record>321</record>
    <time>2012/09/20 16:52:36.126</time>
    <type>Error</type>
    <source>Editor or Editor Extension</source>
    <description>System.ComponentModel.Composition.CompositionException: The composition produced a single composition error. The root cause is provided below. 
Review the CompositionException.Errors property for more detailed information.&#x000D;&#x000A;&#x000D;&#x000A;1) Object reference not set to an instance of an object.&#x000D;&#x000A;&#x000D;&#x000A;Resulting in: An exception occurred while calling the &apos;OnImportsSatisfied&apos; method on type &apos;Microsoft.VisualStudio.Web.Exports.ExportedClassificationFormatCSSKeyword&apos;.&#x000D;&#x000A;&#x000D;&#x000A;Resulting in: Cannot activate part &apos;Microsoft.VisualStudio.Web.Exports.ExportedClassificationFormatCSSKeyword&apos;.&#x000D;&#x000A;Element: Microsoft.VisualStudio.Web.Exports.ExportedClassificationFormatCSSKeyword --&gt;  Microsoft.VisualStudio.Web.Exports.ExportedClassificationFormatCSSKeyword&#x000D;&#x000A;&#x000D;&#x000A;Resulting in: Cannot get export &apos;Microsoft.VisualStudio.Web.Exports.ExportedClassificationFormatCSSKeyword (ContractName=&quot;Microsoft.VisualStudio.Text.Classification.EditorFormatDefinition&quot;)&apos; from part &apos;Microsoft.VisualStudio.Web.Exports.ExportedClassificationFormatCSSKeyword&apos;.&#x000D;&#x000A;Element: Microsoft.VisualStudio.Web.Exports.ExportedClassificationFormatCSSKeyword (ContractName=&quot;Microsoft.VisualStudio.Text.Classification.EditorFormatDefinition&quot;) --&gt;  Microsoft.VisualStudio.Web.Exports.ExportedClassificationFormatCSSKeyword&#x000D;&#x000A;&#x000D;&#x000A;   at System.ComponentModel.Composition.Hosting.CompositionServices.GetExportedValueFromComposedPart(ImportEngine engine, ComposablePart part, ExportDefinition definition)&#x000D;&#x000A;   at System.ComponentModel.Composition.Hosting.CatalogExportProvider.GetExportedValue(ComposablePart part, ExportDefinition export, Boolean isSharedPart)&#x000D;&#x000A;   at System.ComponentModel.Composition.Hosting.CatalogExportProvider.CatalogExport.GetExportedValueCore()&#x000D;&#x000A;   at System.ComponentModel.Composition.Primitives.Export.get_Value()&#x000D;&#x000A;   at System.ComponentModel.Composition.ExportServices.GetExportedValueFromLazy[T](Export export)&#x000D;&#x000A;   at System.ComponentModel.Composition.ExportServices.&lt;&gt;c__DisplayClass4`2.&lt;CreateStronglyTypedExportOfTM&gt;b__1()&#x000D;&#x000A;   at System.Lazy`1.CreateValue()&#x000D;&#x000A;   at System.Lazy`1.LazyInitValue()&#x000D;&#x000A;   at System.Lazy`1.get_Value()&#x000D;&#x000A;   at Microsoft.VisualStudio.Text.Utilities.GuardedOperations.InstantiateExtension[TExtension](Object errorSource, Lazy`1 provider)</description>
</entry>

<entry>
    <record>322</record>
    <time>2012/09/20 16:52:36.202</time>
    <type>Error</type>
    <source>Editor or Editor Extension</source>
    <description>System.ComponentModel.Composition.CompositionException: The composition produced a single composition error. The root cause is provided below. Review the CompositionException.Errors property for more detailed information.&#x000D;&#x000A;&#x000D;&#x000A;1) Object reference not set to an instance of an object.&#x000D;&#x000A;&#x000D;&#x000A;Resulting in: An exception occurred while calling the &apos;OnImportsSatisfied&apos; method on type &apos;Microsoft.VisualStudio.Web.Exports.ExportedClassificationFormatCSSComment&apos;.&#x000D;&#x000A;&#x000D;&#x000A;Resulting in: Cannot activate part &apos;Microsoft.VisualStudio.Web.Exports.ExportedClassificationFormatCSSComment&apos;.&#x000D;&#x000A;Element: Microsoft.VisualStudio.Web.Exports.ExportedClassificationFormatCSSComment --&gt;  Microsoft.VisualStudio.Web.Exports.ExportedClassificationFormatCSSComment&#x000D;&#x000A;&#x000D;&#x000A;Resulting in: Cannot get export &apos;Microsoft.VisualStudio.Web.Exports.ExportedClassificationFormatCSSComment (ContractName=&quot;Microsoft.VisualStudio.Text.Classification.EditorFormatDefinition&quot;)&apos; from part &apos;Microsoft.VisualStudio.Web.Exports.ExportedClassificationFormatCSSComment&apos;.&#x000D;&#x000A;Element: Microsoft.VisualStudio.Web.Exports.ExportedClassificationFormatCSSComment (ContractName=&quot;Microsoft.VisualStudio.Text.Classification.EditorFormatDefinition&quot;) --&gt;  Microsoft.VisualStudio.Web.Exports.ExportedClassificationFormatCSSComment&#x000D;&#x000A;&#x000D;&#x000A;   at System.ComponentModel.Composition.Hosting.CompositionServices.GetExportedValueFromComposedPart(ImportEngine engine, ComposablePart part, ExportDefinition definition)&#x000D;&#x000A;   at System.ComponentModel.Composition.Hosting.CatalogExportProvider.GetExportedValue(ComposablePart part, ExportDefinition export, Boolean isSharedPart)&#x000D;&#x000A;   at System.ComponentModel.Composition.Hosting.CatalogExportProvider.CatalogExport.GetExportedValueCore()&#x000D;&#x000A;   at System.ComponentModel.Composition.Primitives.Export.get_Value()&#x000D;&#x000A;   at System.ComponentModel.Composition.ExportServices.GetExportedValueFromLazy[T](Export export)&#x000D;&#x000A;   at System.ComponentModel.Composition.ExportServices.&lt;&gt;c__DisplayClass4`2.&lt;CreateStronglyTypedExportOfTM&gt;b__1()&#x000D;&#x000A;   at System.Lazy`1.CreateValue()&#x000D;&#x000A;   at System.Lazy`1.LazyInitValue()&#x000D;&#x000A;   at System.Lazy`1.get_Value()&#x000D;&#x000A;   at Microsoft.VisualStudio.Text.Utilities.GuardedOperations.InstantiateExtension[TExtension](Object errorSource, Lazy`1 provider)</description>
</entry>

There doesn't seem to be any specific action that causes this, sometimes it happens when I first fire up VS, sometimes after I leave my desk for awhile and come back. Also, from the log, it appears to happen right after loading the Visual Studio CSS Editing Package. I have MVC4 installed, maybe it's a problem with the new CSS (CSS3 I think?)

Anyways, just wondering if anybody had run into this before and had some sort of resolution.