Robin and Roel Thanks for trying and reporting the results. Both of you and Tim and Dave have run the .py program now (all on hyper-threaded CPUs) and none of you were able to reproduce the problem.
So that indicates that there is something special about our PC. We are planing to re-install Windows XP (and nothing else) and try again. Also, we have one other PC (with a different configuration/CPU) and are planing to do the same to that PC. Olaf -- http://mail.python.org/mailman/listinfo/python-list