Try to boot Fedora 16 or 17 from a livecd
tail -f /var/log/messages
Then plug it in and see what happens.
You might be able to format the drive and lose all your data ;-)
Btw does LVM support removeable drives?
Did you try to add it to your desktop logical volume which might explain the "ghost" drive or did you create a new logical volume for the external drive?