Yes. Is it known that a disconnected/faulty sli bridge causes such issues?
>> Though a faulty SLI bridge is no common thing, and it's hard to improperly connect it, the bridge is necessary for communication between the cards, its absence just kills performance.
Can it be that I connected the bridge "upside down"?
>> No. Easy enough to check anyway ;)
Does it matter if I use the left or right sli connectors (I mean there are 2 on every card for triple sli)?
>> I don't think so, although I have a noname 8800 GTX with a "no parking" sticker on the left connector... Nah, SLI connectors are the same on the left and right.

I was also thinking if the issue isn't that my cards have different clocks.
Forst is XFX with 630mhz core, second is MSI with 610Mhz. But I thought in SLI, they will automaticaly downclock to the slower card.
>> True, so that shouldn't be what's causing the problem. You can always switch the cards for the heck of it if you haven't tried that already.

It is working perfectly if I change the resolution for just one monitor (1280*1024).
>> Aha ! So the problem might just be... poor framerate at high resolutions :/
Did you try a lower TH2G res like 2400x600 ?
Do you have vsync on ?
Did you check the framerate using Fraps ?

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