I have the Asus p5b-plus with the Atheros L1 gigabit adapter and I'm on Windows 7 64 bit. I was getting frequent disconnects when transferring large files over the network or downloading torrents. This required me to run through the troubleshooter each time to allow it to work temporarily again.
I fixed this by going into the driver properties panel> Advanced> Task Offload> Off. After it reset I was running fine.