I noticed that it works with 56 Hz or greater, gtf gives me:
# 800x600 @ 56.00 Hz (GTF) hsync: 34.72 kHz; pclk: 35.55 MHz
Modeline "800x600_56.00" 35.55 800 832 912 1024 600 601 604 620 -HSync +Vsync
I added these lines to my xorg.conf in the Monitor section and restarted X, but it doesn't seem to have any effect, the problem is still the same. I also tried modelines with 60 Hz or more - no success.
Btw: Where do I have to put the "nvidia-settings --load-config-only" so that I don't have to use "nvidia-settings" after each restart of the X server? I tried .xinitrc, but it doesn't work.