I had mozilla, itunes, and limewire running earlier today when suddenly mozilla went into what I call the "spinny-freezy-uppy-thingy" where you can't click anything because the spinner is going and won't stop (this used to happen to me a lot in IE). Usually clicking on the desktop or another program window will allow you to go to the apple menu and force-quit the spinny-freezy-uppy-thingy-effected program, so i clicked the itunes window. But the same thing happened before i could go to the menu! I click on limewire and whaddya know, same thing happens. I switched to the finder and proceeded to close the spinny-freezy-uppy-programs, but when i tried to do that to mozilla the finder spinny-freezy-uppy-thinged! not sure how, but i managed to select finder in teh force quit window and push restart. it went back into spinny-freezy-mode and the entire desktop except for the dock turned blue (the blue you see right before OS X starts up) i was looking at the programs in the dock (there are about 11 of them) and said, "what the hell," so I clicked them all, including the spinny-freezy ones and they all started bouncing. it was great, they just sat there and bounced for a few minutes, then i pushed the restart button and the problem was over.
pretty weird huh, but at least i got some entertainment value out of it.