From http://www.omg.unb.ca/~steveb/linux_tweaking.html
It's an fstab problem:
-You can mount the drive manually as root using the command 'mount /dev/sda1 /mnt/usb_drive' where /mnt/usb_drive has been created before hand.
-That will only allow root write access.
-Adding the line '/dev/sda1 /mnt/usb_drive auto user 0 0' to the fstab file will allow users to mount and umount the drive and have write access.
