I wanted to fix something, and I followed the advice given by someone on the #ubuntu IRC chat. I don't think I did it properly, because now, I cannot even login and I have a black screen. Ii must be a Gdm / Lightdm issue... I am writing this from another computer. Is there a way I can solve this without formatting and losing all my files? All I have is the GRUB menu. I don't even have the recovery mode on the GRUB menu...