I rejigged the OC. Instead of 206x19 I went to 196x20 and that seems to have worked for a while with no crashing.
The other thing I did was turn the fans up to 100% instead of 80%. I know my airflow is crap so maybe even 80% wasn't enough on the cards.
I'll give it a good run when I get home from dinner and see what happens.
EE, I understand the Crysis thing, but Warhead seems fine while FEAR is the game that's freezing on me right now. Crysis wouldn't start so I uninstalled it.
I'm also going to try what Dave says and check out my DX. With all these different games trying to install DX, that could be a problem too. I know FEAR won't install unless you install DX9c with it.
PS: Thanks to all who've chimed in to help so far!