MSI 4870X2 OC Having some problems

[Brownstone]

Hey, long story shot i bought a MSI 4870X2 (Had originally planned to buy a 280)
Thing is... i just installed it seems to work just fine

Minute i load Crysis Warhead my entire PC will reboot (the farthest i go was to press new game, didnt even see loading screen, now it shows EA logo 1 sec and shuts down)... i dnno if it is my PSU (friend of mine has this exact same running a 9800GX2 no probs)
So far only game i tested besides Crysis is Medieval Total War (dnno how valid it is to test it), plays perfectly fine with everything maxed out, unit amount set to huge @ 1920x1200 8xAA/16xAF... not a hitch

Any suggest ? :/ appreciate it

 

[Brownstone]

BTW, my PSU specs




EDIT: Just played around 15 min of Oblivion + Quarl's TP 3 @ 1920x1200 8xAA 16xAF without a hitch -.-

Warhead bench tool wont run either, same shut down... gona try 8.10