What does your /etc/fstab look like. Does it contain the Options for user? 
Here is how mine looks likeounting the windows partition. This is only a 
example, not how my machine is setup.

/etc/fstab
/dev/hda1      /win      vfat     ro,user  1    0

geeze@multi:~$ mount /win
geeze@multi:~$ df
Filesystem           1k-blocks      Used Available Use% Mounted on
/dev/hdb1              9449116   7649024   1312348  85% /
/dev/hda1             10537368   9867512    669856  94% /win
geeze@multi:~$ umount /win
geeze@multi:~$ df
Filesystem           1k-blocks      Used Available Use% Mounted on
/dev/hdb1              9449116   7649024   1312348  85% /


On Tuesday 16 July 2002 08:35 am, Nathan England wrote:
> I recently built a new machine and put slack 8.1 on it and I'm
> having some problems with the mount/umount commans as a
> normal user. man 8 mount says to:
>
> user   Allow an ordinary user to mount the file system.  The
> name of the mounting user is written to mtab so that he can
> unmount the file system  again.   This  option  implies  the
> options noexec, nosuid, and nodev (unless overridden by
> subsequent options, as in the option line
> user,exec,dev,suid).
>
> users  Allow every user to mount and unmount the file system.
> This option implies the options noexec, nosuid, and nodev
> (unless overrid- den by subsequent options, as in the option
> line users,exec,dev,suid).
>
> I have everything the way it was with slack 8, but now when a
> user umounts a zip or a floppy or anything, I get this:
>
> nathan@deadsoul:~$ mount /mnt/zip
> nathan@deadsoul:~$ df
> Filesystem           1k-blocks      Used Available Use%
> Mounted on
> /dev/hda1              4254632   2676500   1358516  67% /
> /dev/hda3             12661560   2126920   9881080  18% /usr
> /dev/sda1                95179        13     90252   1%
> /mnt/zip
> nathan@deadsoul:~$ umount /mnt/zip
> umount: /dev/sda1: not mounted
> umount: /mnt/zip: must be superuser to umount
> nathan@deadsoul:~$
>
> I can't write anything to my floppies or zips unless I am
> root. And I can't unmount anything either. Got any ideas?
> Thanks,  nathan