X hangs

[Rick Marshall]

I'm using FC6 on Thinkpad Z60m.

About once a day X seems to hang. The cursor still works but button 
clicks don't and windows don't receive events. CTRL-ALT-BS doesn't work 
and CTRL-ALT-DEL (obviously) doesn't work.

However the machine still seems to be working.

I haven't got a crash dump because all I can do is power off :(

Anyone else seen this and any ideas on how to fix?

Thanks
Rick

PS I've never had a Unix or Linux m/c behave like this before - but 
maybe I've just been lucky