visual studio 2012 hangs while preparing solution

I am loading a large VS 2010 solution that we are not ready to convert forward yet. This wasn't a problem and the solution loaded fine until yesterday midday. I loaded a solution that had worked earlier that day and it just hung at "preparing solution".

<entry><record>497</record><time>2013/05/20 15:08:01.727</time><type>Error</type><source>Editor or Editor Extension</source><description>
    System.NullReferenceException: Object reference not set to an instance of an object.
    at Microsoft.VisualStudio.Language.Intellisense.CompletionSet.MatchCompletionList(IList`1 completionList, CompletionMatchType matchType, Boolean caseSensitive)
    at Microsoft.VisualStudio.Language.Intellisense.CompletionSet.SelectBestMatch(CompletionMatchType matchType, Boolean caseSensitive)
    at Microsoft.VisualStudio.Editor.Implementation.ShimCompletionSet.SelectBestMatch()
    at Microsoft.VisualStudio.Language.Intellisense.Implementation.CompletionSession.Match()
    at Microsoft.VisualStudio.Language.Intellisense.Implementation.CompletionSession.OnViewBuffer_Changed(Object sender, TextContentChangedEventArgs e)
    at Microsoft.VisualStudio.Text.Utilities.GuardedOperations.RaiseEvent[TArgs](Object sender, EventHandler`1 eventHandlers, TArgs args)</description></entry>

It looks like something about intellisense is broken but I am not sure what could have happened. I wasn't making any system changes (that isn't to say IT could not have, as they push stealth changes at us sometimes). Other 2010 solutions work just fine and I can load the individual projects as well. Others on my team can load the solution also. I've tried repairing my installation of VS.2012 but I am still getting the error. I have deleted the solutions and retrieved them from source control several times and that does not seem to impact the issue.