Distro: Ubuntu 12.04 LTS
GDebi Version: 0.8.5build1
Confirmed Dekstops Effected: KDE 4.11, LXDE, XFCE 4.10
When intalling gdebi on Ubuntu 12.04 LTS the default settings make it impossible to install deb files by double clicking them in a file manager. GKSU will continue to ask for the administrator password over and over again.
To fix this problem open a terminal and type
Change the authentication mode from su to sudo.