onboard nic issues

Hey guys, been trying to figure this out for a couple weeks now, and haven't really been able to google anything close to my situation. So here it goes...

A couple weeks ago, we had ice storms which constantly knocked the power on and off, so after the first set I just left my pc off from there on out.

Problem now though is the onboard ethernet on my nforce 4 board is acting weird. Basically, whenever
my card is under normal internet load it just seems to lose the IP. If I then try to manually release and renew it just sits there and does nothing (trust me I tried waiting)also if I jus reboot the pc, it will just give me a 169. ip; but if I turn the pc off, and hit the power switch on the back of the PSU to cut all power going to the board, wait a few seconds, then power back up its fine until whenever it feels like dropping the IP again. Another wierd thing to add, whenever I am playing online games etc... its fine, it never drops it. Its only when I am online that my download/upload suffers and it acts up.

Further info to add.]
WinXP Pro
431watt enermax psu
asus nforce 4 board, dual onboard ethernet.
athlon x2 cpu
asus 7800gtx vc
1gig of corsair xms pc3200 ram
WD 40g HD