I don't know if he's tried Activity Monitor or not. It's something to suggest.
The hardware test will also intermittently freeze, without revealing anything useful (eg, it doesn't freeze at the same place every time). It freezes on a known good OS X 10.6 and 10.7 install, so it's definitively not the operating system.
Nothing in the logs when it freezes--not surprising, really, because it freezes so hard it doesn't seem to have time to write anything. It'd be a lot more useful if it would panic rather than freezing!
