I get that from time to time with uTorrent. Also using WiFi. If I look at my wireless modem log I can see a high amount of packet errors (outbound). Seems I have this problem if my upload speed is set too high.
If I decrease my upload rate to 50% of what my rated speed is, then no problems. This was the case for me in XP, Vista and 7.
Running wired is a different story. No problems at all. Max upload rate.