My MAc Mini is getting pretty poor LAN performance since the latest round of Windows 7 updates. Coincidentally, a Dell Optiplex 380 in the office had the same problem. A Maplin USB to Ethernet adapter solved the problem. No idea what Broadcom/Microsoft are doing but the network performance over USB2 was far superior to the onboard GigE RJ45 port.
**UPDATE**
After doing a total rebuild of the box, the network is working fine and dandy again. Latest Windows Updates, Bootcamp drivers and it all settled down
