My Pc reboots me every time i try to connect to a map or start bf2142

I have played the game fine for months just fine on 2 different graphics cards with settings set to high quality etc etc, i have stopped playing some time b4 northern strike came out which i still got but only got to try to play now that 1.25 came out . Now what do i get when i try to connect to a map : My pc reboots me !

I reinstall all the latest gfx card drivers set everything to low and try again - no change whatsoever.

Now i uninstall the game reinstall the booster pack and patcher - what happens now is that pc reboots on starting the game , doesnt even get me to menus any more.

Everything else like oblivion , STALKER etc runs fine.

MY PC:
WIn xp latest updates , service pack etc ( fix for the security updatE)
latest direct x

Processor: Intel(R) Core(TM)2 CPU 6300 @ 1.86GHz (2 CPUs)
Memory: 1022MB RAM
CArd : ATI Radeon x850 xt. (latest drivers)

Im completely out of ideas what the hell is going on , only thing that im thinking could have happened is that northern strike screwed up either my pc or the game installation permanently for me? Need help please.