1. Check for spyware. Download AdAware and/or Spyboy Search & Destroy.
2. Replace the cable.
3. Try a different port in the switch or hub.
4. Try a different LAN adapter.
2, 3, and 4 can be easily tested all at once by plugging the laptop in at someone else’s desk. If the traffic problem goes away, one of the three is the culprit and you can do each individually to find out which is causing the problem.