I just got a shiny new mini ipod and apt'd gtkPod only to get the same message as you.
I looked up a manual howto for slackware (i use ubuntu) and it gave me a clue about the cause.
If your iPod is not automatically mounted then this might help..
http://www.linuxquestions.org/questions ... &artid=327
Otherwise if it is and then you get that message when trying to read the iPod in gtkPod then have a look in the folder where things get mounted... on your looks like /mnt, on mine it is /media
My system mounted the iPod as its name (CHEWN THIEF), not as iPod..
debblack@ubuntublack:~$ ls -l /media/
drwx------ 6 debblack debblack 4096 1970-01-01 01:00 CHEWN THIEF
drwxr-xr-x 2 root root 4096 2005-07-05 16:28 floppy0
drwxr-xr-x 2 root root 4096 2005-08-02 12:31 sda
drwxr-xr-x 2 root root 4096 2005-08-18 22:06 usbdisk
drwxr-xr-x 2 root root 4096 2005-07-27 21:40 usbdisk-1
SO now in gtkPod you can go to Edit->Edit preferences
then under the first tab i changed the ipod mount point to
(and it accepted the white spaces)...
Then it worked .. although there is a warning about extended information, but the files appear and i write back to it aswell.
Hope this helps... (although it would have been nice to find some documentation that said this, instead of just listing all the benefits of the program).