I have a Seagate ST380817 (80 GB SATA) in an external Mediasonic HD2-SU2 (USB hard drive enclosure).
It works in Linux but I can't unmount it as a user.
I think KDE/HAL mounts it as root.
I've done a lot of googleing and a hack solution is to add an /etc/fstab entry.
I'd rather fix the HAL configuration to let users unmount it.
My USB memory key mounts and unmounts fine as a user.
You have probably more luck if you'd ask this at LinuxQuestions.org or your $DISTRO forum. Please give me a link to the topic there so I can watch it as well, having the same problem and I'm too lazy to fix it