Started yesterday, not sure what caused the issue. I didn't change anything. (WIN 10 updated to latest build overnight AFTER the issue presented itself)

When I start the game in fullscreen the menu is low res, and mouse does not work. The mouse did work initially, but the cursor was not aligned to the selection. Mouse has since stopped working. I cannot select anything with the cursor.

When I go to video settings using the keyboard, 800x600 is the only res choice available.

ARMA works fine in windowed mode, except that it is VERY slow and unplayable at my normal resolution of 1080p or 1776x1000

Edit:

I have rolled back the video drivers... no change.
Re-installed latest video drivers... no change.
Uninstalled Arma3 and reinstalled... no change.
Restored windows to an earlier restore point... no change. {F27074}