seems like your display manager has crashed or compiz problems also....
PLEASE list your signature in your post. What kind of gpu are you using?? and maybe you need to install drivers for it....
here's a quick workaround:
open a terminal if you can from your desktop by clicking CTRL+ALT+T......if nothing happens goto a tty by pressing CTRL+ALT+F2 and then type:
- Code: Select all
sudo /etc/init.d/lightdm restart
The above command will restart the display manager and see if your panels show up