I am using Emacs 24.4 with Ubuntu 14.04. I just discovered that the C-M keyboard sequences are not working in Emacs. For example in
elisp-mode the key C-M-left is bound to
backward-sexp, but when I press
Ctrl+Alt+"Arrow Left" nothing happens.
If I try
describe-key and type some key combination with
Ctrl+Alt nothing happens, but pressing
Alt+Left works fine. Also pressing
Ctrl+Alt+L locks the computer, which indicates that the desktop intercepts the
Ctrl+Alt keystrokes before Emacs gets them..
I can confirm that the key C-M-r is in fact working, so I think this is an indication that there is a conflict with the Ubuntu desktop keyboard shortcuts somewhere.