Seems to be a problem with the proprietary Drivers a.k.a. Catalyst/fglrx after upgrade.
Reached to a normal functioning login and laptop desktop by the following steps.
From command line mode which I could enter via Ctrl+ALT+F1 during the short flick of a purple background screen before everything freezes :
- enabling restricted repositories, via manually adding to these lines to
deb http://us.archive.ubuntu.com/ubuntu/ precise main restricted
deb-src http://us.archive.ubuntu.com/ubuntu/ precise main restricted
- (re-)installing Ubuntu-supplied fglrx/Catalyst
sudo apt-get update
sudo apt-get remove --purge fglrx*
sudo apt-get install fglrx fglrx-amdcccle
- generating a new /etc/X11/xorg.conf file
sudo amdconfig --initial -f
Still, with that basic configuration dual screens would not work and graphics seem to be a bit upset, amd's catalyst center (
gksudo amdcccle) keeps on crashing when hitting apply. The latter is a known bug under maverick as well, if there is no X11/xorg.conf file present, however, now catalyst seems to crash always)