Heat could be an issue. When my PC started crashing left and right, I reapplied the thermal paste on the CPU and Northbridge and everything's been good ever since. Turns out that the chipset was overheating, not so much the CPU.
I don't think it's a memory problem because when my Mac mini started complaining about bad RAM (and it was a gig stick!), it showed the blinking folder of death. When I put back the original 256MB stick, all was well.
Back on topic: If you're brave and want to void your warranty, go ahead and reapply the thermal paste in the MacBook Pro using Arctic Silver 5. I've done it a few times (because I lifted the logic board up after putting the paste on). Follow the disassembly guides on ifixit.com . My ProBook's cooled down about 5*C (specs in sig).