MBM should not do anything ... are you sure its MBM overheating the system or that its detecting the fact that ur system is overheating? (i.e., what makes you think MBM overheats the system)
When I overclock my barton im scared it will fry what is the likelyhood of this happening
ive got a barton 2500+ OCed to 2800+ and it runs at 49° C (with the stock fan) after playing doom 3 for a couple of hours... so i dunno if thats normal but everyone tells me its good