Update.
After purging 'fglrx' login was successful: sudo apt-get purge fglrx
I tried to reinstall 'fglrx' sudo apt-get install fglrx but after that the problem reappeared so I had to delete 'fglrx' again.
Update.
After purging 'fglrx' login was successful:
sudo apt-get purge fglrx
I tried to reinstall 'fglrx'
sudo apt-get install fglrx
but after that the problem reappeared so I had to delete 'fglrx' again.