Visual Studio: WPF opening a XAML file gives “Value cannot be null”

Question

I recently installed the Windows Phone 7 SDK with an existing Visual Studio Ultimate installation. Now when I attempt to open any XAML file, designer or just XAML, I get the error:

This is for any XAML file; not just WP7. This happens with a brand new project; not just with my existing ones, so I am pretty sure it isn't any funky code Visual Studio can't handle.

Things I've already tried:

• Disabling all add-ons (Resharper + dotCover)
• Complete restarts of machine and VS.

Anyone know with this is; or can suggest other things? Fortunately I was smart enough to image my machine before I installed these tools. I'll roll back to that if I don't get this resolved soon.

Answer 1

Ultimately I ended up restoring my machine to an earlier state. If anyone else runs into this; I hope you have better luck figuring it out than I did. For those that having installed the tools yet, I highly recommend imaging your machine.

Answer 2

Not an answer, but you might get a hint by firing up a second VS2010 instance and attaching the debugger to the first one, and break whenever a CLR exception is thrown (Debug|Exceptions), and then try opening the file with the debugged VS2010.

Damian