I've lost control of Gnome

[dave at tokyocomedy.com (Dave Gutteridge)]

>Look in the Preferences menu.
>

I knew something was wrong. I don't have a Preferences menu! At least 
not anymore. I'm sure I had it before.
I have in the top left corner "Applications" and "Actions". And in 
neither is a "Preferences" submenu.
What should I do to get it back?

Dave