you are confusing mtab and fstab. You shouldn't edit mtab, it contains the list of mounted filesystems, and the system try to unmount all filesystems listed in mtab before shutdown or reboot. (when you change the name in mtab, the system fail to unmount because of the wrong mounting point name).
If any filesystems table edit should be done, this must be on /etc/fstab, that contain the list of partitions and the mounting options.
However, if your storage1000 partition is on a removable device, it's normally mounted by hal subsystem, and you do not need to add it on fstab.
The fact that at mounting, the partition will use the name storage1000-1, is because a storage1000 is probably already in use and already mounted.
May be you have 2 partition labeled storage1000 ? (sda2 and sdb1) ?
try the following command, from a root console, should show all partitions and their labels:
Also note that: /dev/sda2 = second partition of first hard disk, /dev/sdb1 = first partition of second disk.