Accessories menu missing
 

Suddenly, on my Dell Latitude, Ubuntu 10.04, the Applications menu has lost Accessories, and using Preferences - Main menu shows no Accessories entry, though there is an entry for accessories under the Debian heading (but when I tick this the tick disappears when I move the mouse). This is quite baffling and I can't see what might have caused it. Rebooting has no effect.

Thanks for posting your solution and marking it Solved.