dunno what I do really but, after install, reinstall and re-reinstall drivers it is working fine with latest amd_catalyst_11.11c_windows_vista_7.
got to go back on 3.1Ghz, on 3.2Ghz it gets laggy (stock voltage). on Ultra settings works about 60fps but not smooth like I wish, on High settings gets 60-80fps, smooth but not smooth like nvidia cards (have GTX 460 and 560 Ti in the past). My idea with this crossfire was play BF3 on Ultra but it is not enough for it. I will play on High settings, after all to play on High I think with one 6950 or GTX 560 Ti 448 or GTX 570 is enough.