During my several tries to install 12.04 the I could determine the layout of the partitions, format them and start the installations proper. After 53% - 57% of files copied I get a popup like so: "An internal error occurred. Possibly more information can be found in /var/log/messages".

/var/log/messages is not (yet) there, it is a multiboot installation thus I can check. This happens with 32 and 64 bit from two different (dowwnload)-sources. So I stay behind with no clue at all . I could install 11.10 some time ago. Any ideas how to proceed from here?

The first thing you should do with a problem like this is to rule out a badly burned CD as the source of the trouble. When you boot the Ubuntu CD hit the space bar and choose the option to check the CD for defects. If it finds any errors then the CD is bad.
Be sure to burn iso image CDs at the slowest possible speed to avoid errors.

I did check. I tried furthermore two USB-sticks (which I checked as well) from which I started the installation. No luck.

Here is the "solution": http://www.linuxquestions.org/questi...ll-4175412489/.