I beleive there is a 4-pin Molex hard drive power dongle on the video card (eVGA GEFORCE 6800 GT DDR3 256MB DDR 256-bit AGP8X). Maybe you missed connecting a power feed to it when you installed the new PSU? I know you said you checked to make sure it was well seated but you did not say anything about this power connector. I went EVGA's site and the best match to your model may have this extra power connection. I hope this helps.