Hi littlebone, where does the removed mount still appear, in the Library or in the Sources section? For the first issue, just navigate to /mnt/MPD/NAS (from command line or from a SFTP client) and remove the unwanted folder.
Andrea: The 'removed' mount appears in the Sources section. Because it points to a non-existent network directory, it never got mounted and so didn't appear in the library section.
I deleted the mount point directory, but the source still appears in the Sources. But now when I select it, I get the message: "Unable to find suitable address."