Is it possible to read Mac-formatted zip drives?
What device are you trying to mount? You need to mount the 'whole disk' partition, e.g., /dev/sdc, instead of /dev/sdc4 (for a dos formatted zip disk).
Thanks very much everyone. This was the problem. It's an ATAPI drive, so in my case it was /dev/hdd, but really the same.
Thanks, Dave