So I can usually figure this stupid problems out, but this one has me stumped. I'm trying to avoid a clean install of Tiger at all costs...as I'm waiting for Leopard. Ok, I have a 1.83Ghz MacBook Core Duo, and I have the screen set to go off after 3 minutes of inactivity (in the Energy Saver control panel). I have always had it like this and never had any problems. I also have the Keychain menu bar icon showing (the lock), and occasionally choose "Lock Screen" from there if I have very important work on the screen and have to leave, or don't want someone messing with my machine. Now for the problem. Lately, when I leave the computer and go somewhere for a few hours, I come back to see the screen is off (normal), I shake the mouse and the screen comes back on (normal), but OS X is essentially frozen. I can see the new message count on the iChat icon in the dock, and the same for the Mail icon (both apps are running, but hidden). However if I click on an app, nothing happens. The menu bar changes to the app I click on, but the windows don't show up. If I try to launch an application that wasn't open, it gets dark in the dock like when you click on it, and stays like that, never opens. I get the beach ball and then I cannot do anything, except move the mouse around. I'll mention this too -- throughout this whole thing I cannot actually access anything, menu's, spotlight, the Apple menu, cmd option esc, nothing responds. However I can click icons on the desktop and they highlight, but of course I can't open them because the programs don't open. I end up having to force the MacBook off (with the power button) and turn it back on. It runs perfect again, until I leave for a few hours.... If I do the "Lock Screen" when I leave, most of the time when I come back and shake the mouse, the password box comes up and the computer is fine after I enter it. However more and more often, I shake the mouse and see the beach ball, like it's trying to load the password dialog, but it can't. I've left it like this for 40 minutes and the beach ball was still there. This is really annoying me, I've tried most everything I can think of. I repaired permissions (nothing to repair), verified my disk (it was fine), tried changing it to 4 minutes before the screen goes off...and more. Anyone have any ideas?