Sure ... test your line to see how much packet loss there is. It may be at your end (router misbehaving), else a line issue. Else deliberate ISP intervention, since many don't like p2p use because it uses up so much of their bandwidth.

As you said, it happens regardless of computer or version of LW at your end. So the problem sounds as though it's happenning before it actually reaches your network ... somewhere between your router & ISP by the sounds of it.