modem question

[Linda]

I have a  modem set up I use at work where I dial in so I can fix things 
on the network from home. All machines have 8.04.4  LTS, the dialing 
machine uses kermit and the answering machine uses mgetty. The last few 
weeks I have been having trouble with incredibly slow file transfer 
speeds. If I have them shut off the modem and turn it back on the 
transfer speed is back to normal. We changed to a new fax machine which 
shares the line during the same time period.
My thoughts are if the new fax were causing the problem, shutting off 
the modem and turning it back on should not change the situation. Yet 
the timing leaves me wondering.
So do you think the external modem I am calling into is dying or should 
I be looking into other possibilities?
                  Thanks
                   Linda