Some experimental research on HAL automount issues. I've let this posting lie idle for weeks, so I have to rely on my somewhat vague memory here.
4 guinea pigs (Xanthippe, Tisiphone, Archimedes and Hactar), each starting off with openSuSE 10.3. All but Hactar experienced a HAL automount failure for USB drives after a kernel update. Both dmesg and lsusb identified the devices correctly, mounting by hand as root worked also.
A similar problem has been solved in some forums by reverting to an older HAL version, but that one must be prehistoric by now. I fiddled a bit with HAL policies, as explained in this KDE list posting, but with no success.
As it turned out, Archimedes had the gparted issue posted by taaris, what I did with Xanthippe I can't remember (miracle healing after just another kernel/HAL update?), and Tisiphone got a clean reinstall of the whole distribution after even CD/DVD mounting failed - I had additional graphics problems anyway.
So, everything is working again and I have no idea how or why - maybe some rogue update messed with a config file I don't know about...