On ubuntu 12.04 with gnome-classic issuing a "window minimize" operation makes the GUI disappear forever (it's not in the minimized windows list). There's no way to get it back as it's not even in the notification area. I can only kill the process.
Dunno if it's related to #1522 -- I'm using current master branch: 6940626d08e313c5e1cd99c63aeca9da45d5b7a4