I've got the same issues, a few of us do apparently. I think it was the latest nvidia driver update.
i read something about console command d3dmouse something something. it seems to help it. but there was a driver update recently with nvidia and it did cause an issue in another game. after rebooting it was fine in the other game.
I have the same issues. Was fine until I noticed the problem today. I haven't played in a week or so. Maybe there was a patch?