I'm now fairly certain that this problem, and the one in my here.both relate to the same issue, which is a problem with the NVIDIA GeForce GT 330M (or similar) graphics card on mid-2010 15" MacBook Pros running Lion, which has been discussed extensively
Restarting the computer is only a temporary fix. The 'inverted' widgets seem to be a symptom of the much more serious issue of NVIDEA driver related kernal panics.
I'm going to speak in an Apple Genius this Wednesday. I'll report back here later. I've read that some MBP owners with the same problem had to have their logic boards replaced.
Seefor my follow-up to this issue.