After I installed emacs this error occurs every time on startup. It prevents me from installing plugins, e.g. auctex via aptitude. I already tried to install a plugin by hand (rails for ruby), but doesn't work.

The error doesn't contain the message "hostname", but the hostname of my PC is displayed ("bloodredangel-ubuntu"). I changed my hostname to "bloodredangel", but the error message stays the same. While I changed my hostname I saw that in /etc/hostname were two entries:
127.0.0.1
bloodredangel-ubuntu

I already asked this question in an ubuntu forum but they couldn't help. They recognised an misconfigured /etc/hosts file, which I corrected, but from time to time these incorrect configurations get attached by something. I didn't add them by hand, maybe it has something to do with the issue. The misconfigurations looked like this: 127.0.0.1 127.0.0.1
bloodredangel-ubuntu localhost.localdomain localhost
127.0.0.1 127.0.0.1:8080
bloodredangel-ubuntu localhost.localdomain localhost

I didn't found a solution on the internet, so I hope I will find help here finally.