This keeps happening to me, too. I can work for maybe 5 to 10 minutes, and then my cursor will turn into the hand tool and stay that way. Once It resolved itself after several minutes. The rest of the time, I have to leave the program and restart.
One forum response said to delete user preferences. I did that, but the hand tool issue came back within 5 minutes.
Yeah, I was deleting my preferences until that stopped working. The solution is pretty simple. It seems to be a problem after viewing a Flash file fullscreen. Just tap the spacebar to clear it.
Hope this helps. I know how frustrating it is.