I use century tel and with their DSL modem you can use USB or Ethernet. At first I used USB, but one of the techs I talked to strongly recommended that I switch to ethernet.

Anytime you plug in a USB device windows always shows you that Remove hardware safely icon. Its a way of "shutting off" the device so no possible damage couldbe done.

I highly recommend yo use the ehternet portion. I belive you will find that the disconnect problem goes away, and besides I belive its easier to manage when you have a ethernet connection.