Crystal Reports - Random Error

I just upgraded to VS2010 from VS2005, and the built in versions of Crystal for each. I have a form that has the CrystalReportViewer control on it. Most of the time it shows reports (a variety) without any problems. But randomly I get an 'Object reference not set to an instance of an object' NullReferenceException. And it gives me the "No Source Available" screen in VS. I just unchecked the "require versions to match" under debugging, so hopefully it will give me an error location/stack trace.

Has anyone else seen this after an upgrade?

Thanks,
Matt