Ok here's a data point:

I have an Asus P5Q Deluxe with 1201 Bios, running an Intel q9550 (C1 stepping). (TRUE, Corsair 650TX and Asus EAHD 4870, etc.)

Everything is at stock for now (except see below), no OC yet.

I was having failures with P95 with stock settings after 3 - 5 minutes. So I changed CPU Margin Enhancement from Optimized to Performance, and after that P95 worked for hours with no problems. BTW I was having zero other failures -- games working fine (WOW, Assassin's Creed, Mass Effect), etc. No BSODs at all before or after I changed CPU Margin Enhancement. I've only been running all the test suites to establish baseline before OC'ing.