Losing network connection

I have a user that seems to be losing her network connection. There are link lights on the network card and the device manager doesn’t indicate a problem w/ it. I have updated the drivers for the network card. I have changed out cat5 cables. Theonly thing that works when she loses her connection is unplugging the cat5 from the network card and plugging it back in. I feel this is a temporary fix for this problem. Does anybody have any suggestions on what else might could be wrong? Thanks.