have you re-installed windows? Is is it xp or earlier? You may want to save any existing data and then do a fresh os install on your puter. If you are running windows 98/98se or ME a reinstall is a must!!! If XP, it sounds like your driver database is corrupted. Or the card may have taken a dump. if you do a fresh install and "no dice" I would suggest yo buy a new NIC.
Noli Nothis Permittere Te Terere!!
EVGA 680i, Dual EVGA 8800GT'S (650/950), 4 gigs OCZ DDR2 1066, Intel Q9450 at 3.8 Ghz, Koolance Water Cooled, Dual Plextor16x DL DVD+/-RW. Dual WD 250gb 16mb Cache Sata 3.0. 3DMark06 score = 19,168.