Sorry tayral, but I forgot to tell that I have already done that. It seems that your suggestion only prevents a program to start automatically after the disk has been mounted, but it won't prevent the actual mounting of the disk.
I solved it partially by giving all desktop users access to the disk by adding this line to the /etc/fstab file (the relevant options are bold):
/dev/sda1 /media/usb vfat rw,nosuid,nodev,quiet,shortname=mixed,user,gid=mygroup,users,umask=007,iocharset=utf8 0 0
umask makes the device and all files on it group writable. gid specifies a group I created which contains both my desktop users. users is needed so both users can unmount the device.
Now the only annoyance is that one of the users get an error message when the disk is inserted, but that I think I can live with.
This post has been edited 1 times, last edit by "TheThirdBardo" (Nov 30th 2006, 4:04pm)