After the previous upgrades (from 12.10 via 13.04 to 13.10) went without problems, I tried to upgrade from 13.10 to 14.04. 

After downloading it stopped and asked for stopping xscreensaver, I did. Then there were several error messages concerning fontconfig "...out of memory". At one of these error messages the system froze, not even the mouse pointer was moving anymore, nor ctrl-alt F2 was working.

After hardware reset, at boot the system complained about not being able to identify the hardware and only showed a box "what do you want to do".  

What can I do? Does an install from CD make sense? And which one, 13.10 or 14.04?