Perhaps your modem is a PLUG and PLAY modem or a winmodem of some thought ?
> Hi. I'm currently running a Debian 1.3 system, and I'm working on putting > together a Hamm system to replace it. I'm trying to get a ppp connection > running on an external modem plugged into COM2 of the Hamm system and I'm > having no luck. > > First, I defined the connection and then 'pon' to start the connection. > No dice. /var/log/ppp.log contained the following lines: > > pppd 2.3.5 started by root, uid 0 > tcgetattr: input/output error (5) > Exit. > > Ok, I went back a few steps. I pulled down the PPP-HowTo and slog > through the advice it has (which isn't 100% the same as the default Hamm > setup). I discovered that using Minicom, I didn't get any response to AT > commands sent to /dev/ttyS1. > > I rebooted the system and use Lilo to boot MS-Dog. Kermit saw a modem on > COM2 and I was even able to use it to dial my ISP and transfer some more > stuff to my new system. So the modem/serial port/phone line *do* work. > > Back to Linux (stopping by the BIOS setup on the way to note COM2's I/O > address and IRQ: 2f8, IRQ 3). I did a 'setserial /dev/ttyS1': > > /dev/ttyS1, UART: 16550A, Port: 0x02f8, IRQ: 3 > > I searched the mailing lists, and everybody else who was having similar > problems was using Plug-n-Pray internal modems. No responses seemed to > apply to a built-in serial port. > > So I'm stumped. I'm guessing it's a conflict of some kind, but it's a > little too subtle for my experience level. > > Any help would be greatly appreciated. >