I had the same some months ago...
I FOUND a definitive answer on www.linuxant.com.
They offer downloads for HCF/HSF rockwell modems (Conexant) that work pretty much fine on RH8.0 and RH9.0 and also provide a source code driver to compile if the pre-built driver does not match with your kernel version.
Pls read the installation instructions with detail. It is pretty easy.