Windows 7: Problem with Onboard NIC (Gigabyte mobo)

Hi Guys, I'm having a problem with my network card. I have a realtek onboard network card which i have been using for over a year with no problems. Over the weekend i upgraded my psu and gpu now every few hours i lose network connection. What happens is that ill be on the net or playing wow and ill lose connection and i look in the taskbar and the network icon has a X on it and telling me there is no network cable plugged in even tho there is. The only way to fix it is to restart the pc or I have to go into device manager disable the nic and re-enable it and it gets fixed again. The problem is that I dont mind this happening but when it happens in arena I cant get back on time and I dont know why its happening. I deleted the original drivers that came with windows 7 and downloaded the drivers from gigabytes website for my realtek that didnt change anything i changed my cable and ports on the router that did nothing as well but i know it has nothing to do with router or cable because there is 3 other people using the same router and nothing happens to them. Anyone have any idea why this would happen? also power save mode on the nic is disabled before anyone suggests that, this is driving me insane

1st if you still have your old psu, stick it back in for testing in and see if you get the same problem. If the problem goes away then you might have a faulty PSU. If the problem persists with the old PSU then the on board network card might be knackered ... let us know how it goes

Yes I still have the old one, its a 430w thermaltake one and the new one is antec tp 650w. Someone else also told me to update the firmware on my mobo, could that have anything to do with it? and if the new psu is faulty what do i tell em? coz the place i bought it from are really annoying people.