I have just been going through the Service status posts and found this one...
ADSL data transfer problems
12 November 2002
Following the DSL problem that we experienced yesterday evening we have noticed that some our customers are now unable to browse the web or send and receive email.
We are advising affected customers to change their login details to bt_test@startup_domain. Connect to the service, then disconnect and change their login details back to their own details this should then solve their problem.
This problem is due to the customers that were affected by the problem yesterday being connected to BTs test ADSL platform without them realising.