Reset Gnome.
First of all, backup your settings.
mkdir ~/backup_gnome
mkdir ~/backup_gnome/.gnome/
cp -R ~/.gnome/* ~/backup_gnome/.gnome/
Do this with these folders: .gnome, .gnome2, .gconf, .gconfd, .metacity
Another way is to backup ALL of your settings:
mkdir ~/backup_settings
cp -R ~/.* ~/backup_settings/
After making backups, you can delete all gnome settings:
rm -rf .gnome .gnome2 .gconf .gconfd .metacity
WARNING: If you remove all these folders, you essentially remove all the settings.
After resetting gnome, Logout and Login again (or restart your computer). You panels should be restored, now you can edit them again.
I hope this helped you, but try all the answers before mine, because resetting gnome is like reinstalling gnome.
Daniel
By the looks, that's the Ubuntu global menu. To remove it, open a terminal and paste this
sudo apt-get remove appmenu-gtk3 appmenu-gtk appmenu-qt
You may need to restart your computer afterwards. If you wver want them back, simply reinstall the packages.
Best Answer
See this post. It has step by step instructions as well as a well recorded video. He provides a script that can restore your top and bottom panels. Just in case you do it again :)