Originally Posted by AaronP
It sounds like you just don't have a 1280x768 mode in your mode pool at all. Please set the range back to one that would allow the 1280x768 mode to validate (e.g. 47 - 73), start X with "startx -- -logverbose 6", and then generate and attach a new nvidia-bug-report.log.gz.
I have actually confirmed that under Windoze that secondary display's resolution goes all the way up to 1024x1280.
But even when I adjusted the mode settings to that new (higher) rez, I still ended up with 640x480 with the lower refresh rate.
And with the higher refresh rate I can only get into 600x800 VESA mode, I can never get past VESA rez!