I installed a command line system from the Ubuntu Server 12.04 image.
Then I installed on the top of it Gnome-shell along with the applications I wanted to install. Everything is fine with the exception of Gdebi.

When I click on a .deb package to install it, and insert my password I get the message:
"incorrect password...try again".

Does anybody have an idea why Gdebi doesn't get my password?