One more tip, although the previous posts should restore the menu bar which is what you wanted: If you want to restore the panels entirely to the default settings, you can do so by removing or renaming the gconf panel settings folder.
The following command will rename the existing panel folder rather than delete it so you can restore it if you don't like the new result:
If the restart command causes any problems, just reboot. A new default "panel" folder will be created with the original panel settings.
mv $HOME/.gconf/apps/panel $HOME/.gconf/apps/panel-old
sudo /etc/init.d/dbus restart