What am I doing Wrong With SLI?

[fatguy1992]

So the problem is, whenever I SLI my 2x GTX 275's the picture in 3D apps flickers around with the wrong colours. To me it appears that one card is rendering it correctly, then other is using the wrong colours (normally the opposite to what it should be). Sorry not sure if this makes sense, i'm not good at writing. The problem might be that one is a factory oc'ed card, and the other is a reference card. But i'v got friends with cards that run difference stock MHz and their's work fine.

Its happened on 2x different boards (Classified E760 and 790i Ultra), over 6 difference OS's installs (win xp32 and win7 64), different HDDs and every driver I have tried.

What I have Tried...

Tested both cards by themselves, no problem, so its not a dead card.
Neither card is overheating.
I'v clock'ed both at the same MHz's.
Swapping the slots their in and which card is in the primary slot.
Changing SLI cables positions.
I'm out of ideas, anyone got a suggestion?
Disabling PHYX.

Thanks