Parallels 5 VM will not start

I just upgraded to Parallels 5 today and everything was fine with the latest state of my VM.

I used snapshot manager to go to an earlier snapshot. That went fine too.

But then I used snapshot manager to go back to the most recently saved snapshot and got an error message that there was a critical error and I needed to contact support.

Now when I start Parallels the VM window appears with the progress icon spinning as if it is trying to start but it never starts. All of the commands in the Virtual Machine menu appear disabled except the Stop command but pressing that does nothing.

Help!

Thanks!

Tim