That sounds kind of like what I'm going through with my Dad's ADSL line at the moment. It still has sync but appears to be failing to authenticate. The ISP (Plusnet) also can't authenticate with his details on their test line and yet BT have still been sitting on the fault seemingly doing nothing for the last three days.

I doesn't help that I couldn't talk my Dad through using the BT test login. I don't suppose there is a router out there with a web page that has a simple "switch to BT test login and then switch back to my login" option ?