Some time back I added some network disk mounts as Login Items for my MacBook Air (Mountain Lion).
When I'm away from my network, though, I'm constantly bothered by warning boxes saying "Can't connect" to those mounts.
I went to my Login Items screen, and rather than deleting them, I hid them. I failed to understand the +/- buttons and the checkbox.
Now I can't find a way to "unhide" those disk mounts from my Login Items, and successfully remove the automatic mounts.