I am working with Ubuntu as the only operating system on my Toshiba
laptop.

I have been using one of my Nikon D1X Lexar CompactFlash cards in a usb
card reader for temporary backup. So long as I kept it plugged in it was
working fine.

When I removed it from my usb reader and tried to put it back, I got an
unpleasant surprise. Cannot mount volume. The Volume 'Nikon D1X' uses
the FAT32 file system which is not supported by your system.

In the camera I could still see my Nikon photos, but all my backup files
were invisible.

After a day of scanning through the Ubuntu Forums and trying all kinds
of "solutions, I did find one temporary fix.

Restarting from the Live CD allowed me to open the usb compact flash and
see my images.

I don't know what that means, and I am still looking for a permanent
solution.