hehe i tried a few things earlier, latest Gpu z, setting the gen x setting to 'auto' (it was on gen3 before and i've tried gen2 also).
However this is a known problem and Gigabyte are the only mobo maker to officially recognize it, they say it's cause the board is SLI /crossfire capable.
there have been other reported issues with gen 3 nvidia gpus and gen 3 mobos so that's why i think it's cause of your card, basically AMD has more compatibility with gen3 right now.