I have the same problem with Ubuntu Feisty Fawn. I did not have it with previous versions (6.06 and 6.10) Strangely, it is displayed twice on my Gnome Desktop is the external hard drive was already plugged in before I booted. However, if my Gnome session is already started and I plug my external hard drive, it is shown once only. You should notice that when I do 'df -k' my HD (1 partition only) is mounted only once. But Gnome displays it twice on the desktop.
I do not know if it is of importance, but the partition is NTFS. It is read only as this was how Ubuntu 6.06 mounted it and I did not change it since (I have always performed upgrade) -- Partitions on external hd are mounted twice https://launchpad.net/bugs/70380 -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs