I am currently on the highest revision for my motherboard - MSI 760GM-P23-FX (BIOS Revision H.9)

Other MSI users have reported that their latest BIOS updates for the 700/800/900 series of MSI motherboards down-clock them when they are under strain and seem to be having similar problems to me.

I did call my supplier this morning and initiated a return of goods - however I decided to go have a last ditch attempt at diagnosing this, and took a look under the heat-sink. The thermal paste had pretty much dried up to nothing. A generous squirt of thermal compound fixed my problem for about 40 minutes and my temperature never went over 60c despite the strain of playing MGS3 at 1680x1050 at a constant 60fps.

However it did finally throttle and the temp readings of CPUID Hardware monitor read 250c again.

There must be a setting in the BIOS which has the safe temperature set to around 60c - and if it creeps over this threshold I think the Motherboard is overriding the temp reading to 250c, as to constantly throttle the CPU and prevent 'damage'. However I think that might be a little low...

I might ramp it up to 70 if I can find the setting and see if it helps. Also a couple of case fans might help me out here.

Edit: I have played with the BIOS, and there is an option to control fan speed and the ideal max temp allowed - there are preset options in increments of 10 degrees - I have set it to the highest which is 80c. Everything is working fine now, but I don't know if this has helped as I have also installed a pretty meaty extraction fan pumping out the hot air - Max temp has not exceeded 42c so far and I played for a good hour this time.

I will continue to monitor this - and if I have not helped anyone on these forums, at least this thread might get a few hits from people with similar hardware problems searching google.

Thanks all.