IMac suddenly unstable after last security patch

Question

I don't remember exactly when I updated my OS with the last security patch, but I do know that before that time my machine was rock-solid, never crashing. Since that update it crashes about 4 or 5 times per day. Sometimes I get the gray screen of near death, sometimes I simply get a freeze. There's no other new software or hardware that could account for my problems - just the OS security patch.
The crashes appear to be random. Sometimes when I launch Safari, once or twice while reading mail, and several times while the machine was sitting idle. I'm not even sure where to start looking for a potential conflict. It's been a long, long time since I had to diagnose an unstable Mac. Any guidance would be appreciated.

Answer 1

The problems you're describing are identical to mine over the past few weeks. The computer will be running when I walk away. It goes to sleep (all black screen) and when I return and wiggle the mouse the screen will wake at full brightness, but often the clock in the top right stopped minutes or hours earlier. Can't force quit - have to hold the power button to restart.
After much research on a variety of boards, I deleted the InputManagers from User/Library/InputManagers and manually removed others. I've been running Console and individually tracking down each error that seems worth consideration. This topic needs more attention. I've contributed to another thread here:
http://discussions.apple.com/message.jspa?messageID=5476117#5476117