What do you do when pppconfig won't work?

[Guy <guy@remember-tomorrow.co.uk>]

I am trying to set up Debian on a friends computer. I cannot get the modem 
connection (configured using pppconfig) to work. Her modem is a Motorola 
Voice SURFR 56k external on ttyS1. All the info I am supplying to pppconfig 
is correct. The connection is established but only for a few seconds (maybe 
10 secs) before hangup. I use the same ISP and my modem connects no problem. 
There seems to be something strange about the modem, but it is not faulty and 
works with M$ you-know-what.

Anyone got any ideas?

Thanks,
-- 
Guy Heatley