I have a Alctel Speed Touch Home connected to my Mac and it works without any problems in X 10.0.4, 9.2.1, aswell as Windows 2000.
All I have to do to connect to my ISP is:
1. Plug in the modem to the ethernet-card in my iMac.
2. Set TCP/IP to use a DHCP server to obtain a IP-address.
3. Set the 'Search Domain" to "telia.com" (my ISP)
4. Login via a webpage.
Don't know if this helps, perhaps you can specify your problems a little more.