Q:

C#: An exception has been encountered. This may be caused by an extension

I'm running with VS-2013 Ultimate. While executing my code, I'm getting this error message box:
An exception has been encountered. This may be caused by an extension

When entering the log file (the path is mentioned on the message), I'm get this exception:
  <entry>
    <record>905</record>
    <time>2014/08/22 15:46:25.494</time>
    <type>Error</type>
    <source>Editor or Editor Extension</source>
    <description>
        System.NullReferenceException: Object reference not set to an instance of an object.&#x000D;&#x000A;
            at Microsoft.VisualStudio.Debugger.Parallel.UI.ThreadMarkerGenerator.LocationMatchesTagger(DocumentContext location, MarkerTagger tagger)&#x000D;&#x000A;
            at Microsoft.VisualStudio.Debugger.Parallel.UI.ThreadMarkerGenerator.&lt;&gt;c__DisplayClass1.&lt;GetMarkersForTagger&gt;b__0(ThreadMarker marker)&#x000D;&#x000A;
            at System.Linq.Enumerable.WhereListIterator`1.MoveNext()&#x000D;&#x000A;
            at Microsoft.VisualStudio.Debugger.Parallel.Extension.MarkerTagger.&lt;GenerateTagList&gt;d__a.MoveNext()&#x000D;&#x000A;
            at System.Linq.Buffer`1..ctor(IEnumerable`1 source)&#x000D;&#x000A;
            at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)&#x000D;&#x000A;
            at Microsoft.VisualStudio.Debugger.Parallel.Extension.MarkerTagger..ctor(ITextBuffer buffer, ITextDocument document)&#x000D;&#x000A;
            at Microsoft.VisualStudio.Debugger.Parallel.Extension.MarkerTaggerProvider.CreateTagger[T](ITextBuffer buffer)&#x000D;&#x000A;
            at Microsoft.VisualStudio.Text.Tagging.Implementation.TagAggregator`1.GatherTaggers(ITextBuffer textBuffer)
        </description>
  </entry>

I'm sure that this code already worked well in the past.
What could be the reason?

A:

Fixed that problem by deleting the following folder:

C:\Users{username}\AppData\Local\Microsoft\VisualStudio{version-number}\ComponentModelCache

A:

Use the latest update of VS.
Visual Studio exception thrown in Microsoft.VisualStudio.Debugger.Parallel.dll in very rare circumstance

We are happy to let you know that this issue has been fixed in Visual Studio 2013 Update 2.

