I've been having this problem for a while, it is quite frequent, at first I didn't think anything of it, but it keeps reaccuring. For example, two nights ago I left safari, itunes, mail, and adium open. When I came back to my powerbook in the morning, everything was still running fine, however, I could not move or resize any of the windows! The only solution is to quit the apps. When you open the app back up, it opens in the spot you were trying to move it to before you were forced to quit it. Today, after my powerbook has been in my backpack all day (sleeping), I opened up my powerbook in which I had mail and finder open. Mail was working, but it couldn't move anywhere, and finder was stuck also. Very annoying and wierd.