The device is mounted automatically (an icon appears on my desktop) and I don't have permission to unmount it. The message says that only root can unmount this filesystem. As root it works but I would like to unmount as a normal user.
This is the corresponding line on /etc/fstab:
none /mnt/removable supermount dev=/dev/sdb1,fs=ext2:vfat,--,iocharset=iso8859-1,kudzu,codepage=850 0 0