Dial-up connection problem

[superdave1984]

We have a couple computers at work that MUST use a dial-up connection for certain applications. Up until today they both worked fine. Now one will connect one won't. Just decided to not work. The modem is fine because I can hear it dial, the screeching starts, but then stops after a couple seconds. It also dials fine for another app they use. Then it gives me an error like didn't recieve a reply or something. The other one screeches for several seconds and still works fine. I have uninstalled the modem and drivers, no luck. They are both configured exactly the same. It has to be something to do with the thing not completeing the handshake. Same phone number dialed from both. They use the same program, same user ID and password. They are not trying to connect at the same time either. Dedicated phone line just for this connection and it works fine as well. Unless there is a problem with authentication I can't figure this one out. And I really don't want to reinstall the client. Suggestions other than ditch the dial up?