[Head_Unit]

2.1GHz intel, Core2 Duo, last of the white iMacs. Just got this from eBay.

Seems great...until after sleep, when it might run a few minutes and then inevitably freezes, necessitating holding the power button to shut down. sometimes the freeze starts in one app but then spreads to all. Force Quit (Option-Command-Escape) does nothing.

Googled a lot; seems no confirmed broad fix, which is why I wonder if it's hardware related.

I was intending to change from Snow Leopard to Lion and install a bigger HDD. BUT before I do that, is there any non-tiny chance this is HW related? Because if it's hardware, forget it, I'll just return the machine.

[Big Mac]

I would suspect the hard drive personally. When the beach ball spreads from one app to the rest, my assumption is a disk access hang.

[Waragainstsleep]

Does the system log tell you anything?

[Sosa]

Run disk repair, try reinstalling the OS. It worked on my old 12" Powerbook and I also think it was the hard drive leading to frequent kernel panics if I tried to reboot.