Windows 7 - RIP Q6600? 5770? or someone else?

HALP!

I think I've broken something or something needs to be taken off the caffeine so it speaks to me again.

I've got a Q6600 running on a X38-DQ6 with a pretty much spanky new Vapor-X 5770. Now it's been dropping me out of MW2 like it's overheating after a couple of hours or something. I check my temperatures more regularly than a banker checks his bonus scheme so I very much doubt it has anything to do with heat.

After a little research I got to reflashing the BIOS (Windows said something about a firmware problem and I figured it'd remove any configuration issues) and then I started running 3DMark 06 to test the rig in various setups. I figured it was a problem which happened only when the memory, CPU and GPU were under load (Prime95 runs on all 4 cores so happily I can game with it running in the background... or I used to be able to until games started crashing on their own) so I fired up 3DMark 06 and to begin with it motors along then, almost like a cache had been filled and was being purged, it halts, stutters, drops to like 6fps and then resumes it's previous speed.

After dropping to desktop a few times my max temperatures are fine, the voltages are within less than .1 of a volt... I can't figure it out.

Oh and whilst I remember, Core temp seems to think that my quad core can independently clock back it's cores. I didn't think it could do that being a lowly Core2Quad?

Also I've tried these runs with no overclock, with and without temperature control and with the graphics card set up with overclocks and stock speeds. It always happens the same way. Like 10 seconds of no problems, then stutter, then run fine for another maybe 6 seconds, then stutter, then fine etc etc...

Now am I looking at a new CPU etc or is this just a simple fix?