ISP servers, dialup problems

[jimmy]

I have been using dialup and usually there is no problem, and I connect at about 49,000 bps. For the past week I have had almost no success in getting good connections. The speed has been about 21,000 bps, often disconnecting after about a minute, and getting error messages such as authentication failure (check password) or modem error messages (check configurations).

I had my computer and modem checked and no problem was detected. The ISP said that often the lines are congested or there might be a problem with my telephone wire. The computer guy suggested that ISPs use many servers, they sometimes discontinue servers and some of them are slow (not congested?) He said the best thing to do is re-try connecting immediately and see if I can get a better speed, about 49,000. My internal modem is 56K. He also said check my telephone line. I called the telephone company and they tested from their offices, saying there is no problem there.

My questions: What would you think is the most likely explanation? How does a single dialup number access multiple servers within an ISP? (I don't understand that) Do you think its the telephone wire or the servers? Thank you!