I tried the following to solve the problem:
- different display driver (310.90; 314.22; 327.23; 337.88)
- Microsoft Fix it 50848 (http://support.microsoft.com/kb/2665946/en-us)
- set PCI-E energy save options off
- set nvidia 3d energy mode to max performance
- window mode
- less gpu and gpu-ram clock (underclock)
- less cpu clock (underclock)
- motherboard bios update
- clean the graphic card because of temperatures (max 85°C)
- furmark gpu stresstest (runs OK)
- heaven gpu stresstest (runs OK)
- heavy load cpu/ram stresstest (runs OK)
- memtest 86+ ram check (runs OK)
- check a lot of other games (all games running fine!)