valec06: what was the exact flashing procedure that you used?
I guess at this point, one thing to try is reinstalling the driver (such as 258.96). But what was the exact flashing procedure that you used?
The BIOS is actually located here:
GTX 400 Overclocking/Modding Thread
Of the two that are available, I recommend the EVGA Identifying - 1.15v max. version. Not only is this the ocx480 BIOS, but between the two available, it's the one that has given me better results. So, give it a shot and see what happens!