There is an issue with your current network configuration.
Go back to the Desktop, right click on "Network Neighborhood" - "Properties." The Network Configuration window should pop up. In the white box, check for any duplicate TCP/IP or any duplicate hardware adapters. Leave only one and delete any extras. Reboot. You should run another Line Quality test to see if the problem persists. It shouldn't, but it's always good to check.
Another thing for Windows users to do is to have your NIC (ethernet card) installation disk handy, load into Windows Safe Mode, delete all the hardware adapters and start from scratch.
If you do not know how to enter into safe mode and make changes, just start a new topic asking for assistance in our Microsoft Help Forum.