It seems this is because Ubuntu patched gnome-settings-daemon/gnome-control-center to use GConf for keybindings. This causes all built-in shortcuts to not work at all, and the custom shortcuts to misbehave when using the "Meta"-key.
There is a bug at gnome bugzilla for the meta-key-issue: https://bugzilla.gnome.org/show_bug.cgi?id=659899
I summarized the workarounds here: http://hacksr.blogspot.co.at/2012/06/gnome-34-in-ubuntu-1204-and-keyboard.html
It seems this is because Ubuntu patched gnome-settings- daemon/ gnome-control- center to use GConf for keybindings.
This causes all built-in shortcuts to not work at all, and the custom shortcuts to misbehave when using the "Meta"-key.
There is a bug at gnome bugzilla for the meta-key-issue: https:/ /bugzilla. gnome.org/ show_bug. cgi?id= 659899
I summarized the workarounds here: http:// hacksr. blogspot. co.at/2012/ 06/gnome- 34-in-ubuntu- 1204-and- keyboard. html