My native resolution is 1920x1200, this is what xrandr gives me:
    Screen 0: minimum 8 x 8, current 1920 x 1200, maximum 16384 x 16384
    DVI-I-0 disconnected (normal left inverted right x axis y axis)
    VGA-0 disconnected (normal left inverted right x axis y axis)
    DVI-I-1 connected primary 1920x1200+0+0 (normal left inverted right x axis y axis) 518mm x 324mm
       1920x1200     59.95*+
       1920x1080     60.00  
       1680x1050     59.95  
       1600x1200     60.00  
       1440x900      59.89  
       1280x1024     60.02  
       1280x960      60.00  
       1280x720      60.00  
       1024x768      60.00  
       800x600       60.32  
       640x480       59.94  
    HDMI-0 disconnected (normal left inverted right x axis y axis)

I use wine with an application, which changes the resolution. After that I'm unable to change the resolution back to my native one with xrandr. It still lists the resolution but 'xrandr -s 1920x1200' says it is not found in the available modes. 'xrandr -s 0' changes succesfully back to 1920x1080 (resolution 1).

This stays the same, until I use 'nvidia-settings' to change back my resolution. Then also xrandr works again.

I use the proprietary nvidia driver (352.41) with xorg (1.17.2 (11702000)). But I have this bug already a long time, across different linux distributions and hardware (all nvidia though).