Thanks, David for your efforts. I don't need to see your PDFs. If also your n=512 experiment runs through I would conclude that the problem is not with the code. I plan to upgrade soon to the most recent version of Mathematica and, when this is done, will try again this notebook to see whether it then works as it works for you.
As I wrote above, I have a working version (on my system) for further development of the simulation.
Of course, it is very desirable to get a hint concerning the reason for the failure on my system. It would be very helpful if a Wolfram-expert would give his oppinion on the most probable ocurrence of a message:
"The kernel Local has quit (exited) during the course of an evaluation"