So, I installed wicd to manage my wireless network, tried to find it in system services to make it start up automatically, it wasn't there so I decided to reboot and see if then it would appear. For my surprise I wasn't able to log in to GNOME again, or any other desktop I have installed.
When I log in selecting any of the desktops from the drop-down list all I get is this:

What should I do?
I'm kind of new to Linux and I have no idea of what could have caused this.