I run GNU/Linux and the issue that I had with a Novatel in ExpressCard is that it would emulate a virtual CD-ROM and I'd actually have to 'eject' the CD-ROM before I could treat it as a data modem. I recall I'd dial #777 and go forth and conquer with a PPP connection.
I recall the solution being to modify how udev handled the device so that it would automatically "eject" the CD-ROM and treat the device as a modem. I suspect this is the same issue you're running into, albeit with a mass storage device and not a CD-ROM.
$ cat /etc/udev/rules.d/99-novatel.rules
#Jan 20, 2010. Eject on insert emulated CD-ROM
ATTRS{manufacturer}=="Novatel Wireless Inc.", RUN+="/usr/bin/eject /dev/%k"
This is how I handled the issue, if USB Mass Storage isn't important to you, perhaps you could modprobe -r usb-storage. Hmm, doing some research as I compose this it looks like you can perhps use usb_modeswitch (»
ubuntuforums.org/showthr ··· =2036043) if the 'eject' doesn't work for you.
Coupling the correct 'eject' or 'modprobe -r' command to the above udev 99-novatel.rules I posted might would make for an automated solution.