Hi Pete,
I'm just posting to let you know that I had exactly the same issues as Lee and others.
I could'nt fly for any longer than an hour before the sim would hang, and sometimes CTD and occasionally reboot the machine. I tried eveything (but not as extensive as Lee) and could'nt put an end to it.I almost gave up flying altogether. It was just by chance that I located this thread and tried ver3.70 and have been crash free ever since. In fact, I flew for 10 hours non stop without a problem last night.
So, just some more info for you. I'm running an invidia geforce 7800gs,3.0gig proc.,2 gig ram, with PMDG, Wilco,UT,FSGenisis, and a few more.
Regards, Ron