[K12OSN] Set global screen resolution

[Hung Phan]

Hello, folks

We are currently having issue with some clients screen flicker and the everything on the login page appear as double. The login screen logo is showed as K12LINULINUX. Same symptom for the desktop. We can change the screen resolution to 1024x768 60Hz refresh rate and the desktop appears normal again. When we first open Screen Resolution, the monitors listed as Unknown and have the resolution at 1600x1200 with 75Hz refresh rate. These are Sony 420GS.
How do we fix this issue? Install video driver? Set all clients screen resolution to 1024x768? Usually this setting is under /etc/X11/xorg.conf but it is no where to be found.

Thank you for any advice,