Btw. I know that other guys too have this problem, I read about it at least once here and on www.heise.de
another user mentioned this problem.
Another configuration which works ok for me: Duron800 with GF5200
I simply can't see any reason except a bug why a Duron800/GF5200 should outperform an Sempron-1.8ghz/GF6600 by at least a factor of 5-10x.