I believe by default they will just grab an IP on the WAN side from your ISP and then pass out a DHCP IP on the ethernet/USB ports to you. I bet you need to tell linux to use the USB for the network connection. Have you checked that yet? Are you using the beta redhat 9.1 right now. open a terminal window and see if you got an IP address from the modem. try the ifconfig command.

Not that you asked for it, but here's some old school tricks you can try once your computer is talking to the cable modem corretly. type http://192.168.100.1 in your browser to pull up a cable modem internal reference page.

Here's another nice link with some uncapping software. the key word is "tcniso". I don't advise doing it, but its interesting info. If your ISP catches you, they'll probably ban you.
http://www.iggyz.com/TCNISO2.html
http://www.iggyz.com/book/cable.html

Critter

http://www.chrisstokes.com