Okay... another keyboard mapping question with Unity (2D) in Ubuntu 12.04.
I use org-mode in Emacs daily. It uses Alt-Shift-LeftArrow to promote a subtree (move it one level to the left) and Alt-Shift-RightArrow to demote a subtree.
Alt-Shift-LeftArrow works perfectly.
It seems that Emacs never receives the key combination Alt-Shift-RightArrow. That is, if I ask for help on a key binding (ctrl-h k ... keys...), Alt-Shift-LeftArrow also the appropriate help page, but Alt-Shift-RightArrow does nothing at all.
I suspect this means that Unity is swallowing Alt-Shift-RightArrow and refusing to pass it along to the application that has focus. Further evidence: Using the SuperCollider programming language, I can have it print something on every keystroke received by a Qt GUI widget. If I do Alt-Shift-LeftArrow, I get three events, one for each key. If I do Alt-Shift-RightArrow, I get events for Alt and Shift, but not the arrow key. Therefore, the issue is not specific to Emacs. Something system-wide is killing this particular key combo.
I've checked the system settings Keyboard control panel, and there is no active keyboard shortcut for Alt-Shift-RightArrow. So... where do I look now? (I mean, where do I look apart from switching back to the Gnome desktop...)