For some unknown reason, all of a sudden I am losing my finder. Well, first my desktop is missing something that I just put there... Then, I try to relaunch the finder, command-opt escape, and I see that the finder is not responding and it won't relaunch. Of course, with no finder, there is no menu bar at the top and no way to safely shut the machine down. So, I hold the button down until it shuts down... wait a few minutes and restart.
I have repaired permissions several times, but this is happening a couple of times a week now and more often than seems right.