I have the same problem. In my case, it is due to stray gnome processes that aren't killed properly by <ctrl>-<alt>-<backspace>. Logging out and killing them from a text prompt fixes the problem.
See bug# 126719 -- Brightness applet fails to function after restarting X server https://bugs.launchpad.net/bugs/112751 You received this bug notification because you are a member of Ubuntu Bugs, which is the bug contact for Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
