"...USB support under Linux seems to be pretty decent from
kernel version 2.2.18 onward. The newest 2.4 kernel obviously has
the most up-to-date support and is recommended if you have problems
with your current kernel version."
"The first thing to do if you're using Linux and want to use
a USB modem is to check your kernel version and decide whether a
kernel upgrade is needed. In an ideal world, you would be using the
latest 2.4.X kernel, but anything after 2.2.17 should be fine.
You can check your kernel version by typing uname -a at a shell
prompt." "If you have to upgrade to a new kernel, you'll have to go
through the usual procedure of configuring, compiling, and
installing it. While configuring, make sure that you select the ACM
modem driver. Linux-USB.org has published a how-to guide describing
some of the details of this procedure. Depending on your kernel
version, there will be many different USB selections."