READ THIS if your finder is crashing/looping/closing folders!!!
and you have to click back into the program you are using) after the last Apple Security Update that caused this bug.
I do not know if this will work for everyone, but it worked for me.
It seems all to be linked to Stuffit and a preference called Stuffit AVR (Archive Via Rename): In your system preferences go to the bottom and click on the Stuffit AVR option. Click the Stuffit AVR tab
on the left, and click the "STOP" button. This should do the trick. For some reason this is cycling through our desktop/finder and causing so much of the frustration since this update.
Hope this helps!
G5, Mac OS X (10.4.11)