Para corrigir:
monitor 1 (24 ", 1920x1080): monitor 2 (22 ", 1680x1050):
informações sobre os monitores:
$ xrandr
Screen 0: minimum 320 x 200, current 3600 x 1080, maximum 8192 x 8192
DVI-0 connected 1920x1080+0+0 (normal left inverted right x axis y axis) 531mm x 298mm
1920x1080 60.0*+
1280x1024 75.0 60.0
1152x864 75.0
1024x768 75.1 60.0
800x600 75.0 60.3
640x480 75.0 60.0
720x400 70.1
DIN disconnected (normal left inverted right x axis y axis)
DVI-1 connected 1680x1050+1920+0 (normal left inverted right x axis y axis) 473mm x 296mm
1680x1050 60.0*+
1280x1024 75.0 60.0
1152x864 75.0
1024x768 75.1 60.0
800x600 75.0 60.3
640x480 75.0 60.0
720x400 70.1
Comando que realmente define o monitor:
$ xrandr --auto --output DVI-0 --mode 1920x1080
$ xrandr --auto --output DVI-1 --mode 1680x1050 --right-of DVI-0