Check to make sure both the card and the switch port are set to the same speed and duplex settings. I would think that both should be set to auto. If they are mismatched you will have issues. You should also connect directly to the card via a cross-over cable. Again, pay attention to the speed and duplex settings. This will tell you with more certainty if you have a network issue. If you still have the problem, try a second laptop to confirm that it is not your machine. If problem still persists, try changing the transceiver. If you still have the problem, I would think all there is left is to look for a firmware upgrade or card replacement. If you still have a problem, just quit and find a new place to work.......
Hope this helps
Rob