Well I got a few suggestions...
1. (Looks like you did already) Goto http://www.linmodems.org and verify that your modem will work under
Linux and download any drivers if needed.
2. When you get to your bash prompt type setserial -a /dev/ttyS*
(replace star with a number, 0 is com1, 1 is com2, etc...)
When you see a port with 16550UART in the little descriptions you get, there is your com port
3. you then set up wvdial to access that com port through /etc/wvdial.conf
After you get the setserial thing going, come back here and let me know what happened.....we might try something else if that doesn't work.