My mate joined up to BT B'Band and had problems with it also.

He could install the driver etc and set it up and get it working, then after 10mins or similar it would not connect to a web page and the phones wouldn't work

On a hunch I put a DSL filter on every phone line in the house (4 I think) and it worked after that. Took em all out and only used the one where the ADSL modem was plugged in and it worked, then didn't work.

So I refitted every phone line with a DSL filter even tho only one had both phone and ADLS plugged in and it has worked fine ever since

Much oddness......