SLi screen tearing

My 9800gtx sli has been fine for a while, untill last weekend.
I hadn't actually played any games recently, however now I'm getting screen tearing on any game I play, also on 3dmark05

I updated my drives just to check, 257.21 WHQL, still there. :(
I removed the drivers and rivatuner just incase, rebooted into safe mode, ran driver cleaner to fully remove all traces.
Rebooted and reinstalled 257.21, still there :(
Moved my sli bridge to the other connectors, still there :mad:
Reinstalled rivatuner, underclocked both cards and changed the fan speed to fixed 100% (my they are loud) still there :mad:
Tried monitor via a d-sub cable and DVI to d-sub adaptor, still there :rant:

Just bought a new sli bridge off fleabay just incase but I'm stump out of ideas.

Happens on any sli mode, normal or ether of the 2 alternate frame render modes
Ether card on it's own works fine, Force Vsync on and I get less tearing but still bad enough to make games unplayable. :(

Not sure if it'll help, but you could try resetting your BIOS CMOS incase something funky is going on with PCI-E lane allocations.

Well an update on this, I booted into my my old windows7 beta and apart from it complaining about it not being a beat and so not activated or valid, sli is as smooth as slik, not the slightest issue with 182.57 drives

I got my new sli bridge, a hard one, installed that not change in win7beta still smooth still tearing so much it's unusable in xp :(

I can only conclude it's shoddy xp drivers :rant: