Re: nvidia driver crash when starting X
The config file itself looks ok. The only real difference I see is the resolution validating part. In the case it "works" you gave:
HorizSync 31.5 - 48.5
VertRefresh 50.0 - 70.0
And for the case it doesn't:
HorizSync 30 - 70
VertRefresh 50.0 - 130.0
Normally it doesn't really matter if the the values you entered are 100% correct as the drivers validate what you entered. As there's further no rreal difference I would investigate if this causes problems after all, so really use the correct refresh rates.
Further check if there are no errors in for example /var/log/messages.