Same thing is happening to me,when I first logged in today, I setup video options, an it was fine. But when it told me to run the game to enable new settings. it defaulted my video to 800-600, an now my mouse wont work in game. When I try to change video settings back to 1920-1080 it crashes to desktop.

EDIT*
I found this problem is solvable, by switching to Window/fullscreen mode before you play, then it defaults to the correct resolution.It also strangely enough fixes the mouse issue.

Please do not copy paste text files to Notes. Thank you. Millhauz