So I removed the password of my user account and restarted. When I tried to login, a black screen showed up and took me immediately back to the login screen. Running Ubuntu 11.04 via LiveCD, I found the /home folder is owned by root, no idea if it has to do with that. I also checked the option to encrypt the user folder at installation, propably wasn't the best idea.
I can login with ctrl + alt + f1, when I then try to start x, it gives me the error message, that .Xauthority is missing. Now I wonder how I'd create that file, when I can't access my /home/user folder, because it is encrypted. It also tells me on login that I should run encryptfs-mount-private.