Comment 3 for bug 856810

I had a second look at my syslog output and noticed the following line:

lightdm main process (1154) killed by TERM signal

I replaced the lightdm with gdm:

sudo apt-get install gdm

...and after that the login screen comes up just fine with gdm.

Thus it seems this is not network related after all. It is confusing that the network related error message remains on the screen forever when it is lightdm which seems to be the problem.