With today's updates to 12.04 I can no longer bind gnome-do to either ctrl+alt+space or super+space. With 11.10 it wasn't possible to use super+space, on a fresh install of 12.04 super+space was working properly.
Today it stopped working, if I try to bind control+alt+space then the controlkey shows up in the keyboard binding as Primary.
I am running Unity, which in the past blocked super+space, it seemed to have stopped blocking it on 12.04. It shouldn't affect ctrl+alt+space.
Configuring either binding produces the following error in the gnome-do output:
libdo-WARNING **: Binding 'space' failed!
libdo-WARNING **: Binding 'space' failed!
I'm stuck binding to shift+alt+space.
Best Answer
This is a combination of two problems:
The super problem is that Unity recently changed to grab the super key entirely - until version 5.6.0 it wolud pass on super keypresses that it didn't use to other applications that had registered bindings, like Do.
The second problem is due to a change in GTK - it's bug #903566 in Do, which is fixed in 0.9 and in Precise. You can temporarily get a fixed Do from the daily builds PPA.