Not the first time I accidentally delete it happens that one of the panels of my Ubuntu desktop. The solution, once known is simple. We use a terminal and type the following commands in it:

gconftool-2 --shutdown
rm -rf ~/.gconf/apps/panel
pkill gnome-panel

After a few seconds we regenerate all gnome panels.

Sure it could be that you can not access a terminal under these conditions, not by chance that we deleted a panel and may be the above, the application menu. Then create a launcher by clicking the right mouse button on a free desktop. Dialog box appears and "Name:" write terminal and "Command:" write gnome-terminal . We accept. Now you can open a terminal by that pitcher.

Update: More easy to open a terminal by pressing [Ctrl-Alt-t] simultaneously.