main menu dissapeared

Thanks for your question. It is likely that gnome-panel has crashed and was unable to bring itself up again. Press Alt+F2 to open Run dialog, type "gnome-panel" and press "Ok". If it works, let us know; if it doesn't, don't hesistate to ask more help :)

Tried this a couple times...I get this message: "I've detected a panel already running, and will now exit."

Well, let's try something else. Again, press Alt+F2 to see Run dialog, but this time, type "gnome-terminal" to open Terminal.

Then, type "killall -9 gnome-panel" and press enter. Wait a little bit (couple seconds or so) and press ↑ to do it again. If Terminal says "gnome-terminal: no terminated processes" (translated from Finnish version, actual message might be a little different), gnome-panel is successfully killed. Then type "gnome-panel &" and press Enter.

No, for some reason this isn't working either...I did what you said but nothing happens, I don't get the message "gnome-terminal: no terminated processes" or anything at all, it just goes down to a blank line, or repeats what I typed.

If you still have the lower panel, right click on that, and then click "New Panel" From there you can move it back to the top of the screen, right click, and select "Add to Panel" and add your menu bar, system tray, clock, etc.

Hope this helps,
Justin