Actually the logfile is quite clear:
(WW) (1600x1200,Monitor0) mode clock 175.5MHz exceeds DDC maximum 170MHz
(WW) (1600x1200,Monitor0) mode clock 189MHz exceeds DDC maximum 170MHz
So basicly your modeline is not correct according the nvidia driver also note that the driver complained about bad vsync ranges for both screens
II) NVIDIA(0): Processing requested modes for display device DFP-0:
(II) NVIDIA(0): "1600x1200_DVI"
(WW) NVIDIA(0): The user specified VertRefresh "30.000-85.000" has been
(WW) NVIDIA(0): adjusted to "50.000-85.000" (the intersection with
(WW) NVIDIA(0): EDID-specified VertRefresh "50.000-85.000"
(II) NVIDIA(0): Monitor0: Using hsync range of 30.00-92.00 kHz
(II) NVIDIA(0): Monitor0: Using vrefresh range of 50.00-85.00 Hz