Horrible Mac Troubles

Hey,
I have had my 24" 2005-2006 model iMac for about three years. For the past couple of months I have been having horrible problems with it. Highlighting icons on the dock can lead to a crash, which then may 'spark' multiple crashes. There are many simple ways to set off a crashing spree, and even when I have just one small program open the whole computer usually crashes. I have been monitoring all local processes and network connections and everything is seemingly fine! On top of it all, I get constant graphical glitches that consist of skewing, multicolored lines and/or patches filled with static on my screen. I usually deal with up to twelve crashes in one small session (believe me, I have counted) before I just give up on it. My boot time, which was seconds when I first got the machine, is now a sluggish three minutes. What's wrong, is my Mac on its deathbed ? Thanks.

Well, I am by no means a pro, but have you booted from the OS cd and
ran disk utility? I would verify premissions and then verify the disk. I just
did this to my G4 as I was experiencing frequent program crashes and a slow
machine. I had quite a few problems and was able to fix all of them by doing
this. Not sure about your display problems. Good Luck.

Sounds similar to this issue. Do you find that when it's crashed, bits of the system still work? On my imac, after the screen has gone nuts and it appears to have crashed, I find I can still log in by SSH and issue a shutdown command to power-off normally. It's very odd. Much google-ing seems to suggest it's perhaps dodgy graphics boards, possibly due to overheating.