Hi, perhaps the problem is that the main monitor has a lower resolution than the secondary one.
Command# xrandr Screen 0: minimum 8 x 8, current 3600 x 1080, maximum 16384 x 16384 DVI-I-0 disconnected (normal left inverted right x axis y axis) VGA-0 connected 1920x1080+1680+0 (normal left inverted right x axis y axis) 531mm x 299mm 1920x1080 60.00*+ 1680x1050 59.95 1600x1200 60.00 1440x900 59.89 1280x1024 75.02 60.02 1280x960 60.00 1152x864 75.00 1024x768 75.03 70.07 60.00 800x600 75.00 72.19 60.32 56.25 640x480 75.00 72.81 59.94 DVI-I-1 connected 1680x1050+0+0 (normal left inverted right x axis y axis) 474mm x 296mm 1680x1050 60.45*+ 59.95 59.88 1600x1200 60.00 1440x900 59.89 1280x1024 75.98 75.02 60.02 60.02 1152x921 65.85 1152x900 66.00 1024x768 75.03 70.07 60.00 800x600 75.00 72.19 60.32 56.25 640x480 75.00 72.81 59.94 HDMI-0 disconnected (normal left inverted right x axis y axis) I patched the problem by adding the following lines ### MARCO INIZIO ### GRUB_GFXMODE=640x480 # Hack to force higher framebuffer resolution GRUB_GFXPAYLOAD_LINUX=640x480 ### MARCO FINE ### in /etc/default/grub (and runingn the update-grub command) Thx Marco Righi