This might give you a clue, but there could be many other reasons.
I had the same message from a dial-up user yesterday, they were using an
incorrect password.
Mervyn Jack
Technical Services
Country Netlink Pty Ltd, Cobram, Vic, Australia.
Providing Internet access to the Cobram and Shepparton local call areas.
Phone 058 711000
Fax 058 711874
Mobile 019 438419
IRC nick JtRippa