Sorry to report a follow-up to my post on 15/03 - I still have the problem after Win7 SP1. It just took a few days to materialise. I would say it seems to happen less often than before but still not fixed.
I'm not clear on why it's ok sometimes and not others!
Yes it's really an annoying bug, regardless which software (MP or Win7) is producing this error. It would be nice if the team could get in on the bugtracker and fix it as fast as possible.