From time to time I experience a similar problem on dialup. It dials,
then the handshake begins for about 1 or 2 seconds and then quits. And
this will repeat until I plug into another phone line. Then my problem
stops. So plug a phone in and see what you get. I eventually found out
the phone company had a almost severed wire which caused a great amount
of static on the line. To compound my problem is I live out in the
country with a not so hot phone company.