For some reason, sometimes when I log in the top panel applets appear garbled. For instance the session applet is missing its icon, and the current username is repeated twice. This doesn't happen very often, but when it does the session applet is not responsive so I can't get to the log out menu option.
Is there any other way to log off the current user other than using the (non working) session applet?
Press Alt+F2, type
gnome-session-save --logout
, then hit enter. If an application is blocking logout, trygnome-session-save --force-logout
If you enable Ctrl+Alt+Del, you can use that to kill the X server, which will log you out. To enable this, go to System -> Preferences -> Keyboard, then go to the Layouts tab and click Options. Expand the "Key sequence to kill X server" and check the box.