@Hylander

I had some mouse issues when I plugged in a joystick. By default, the 'on-foot' control menu has joystick key mappings, and the game wanted to override the mouse/keyboard in favor of the joystick mappings. My character was constantly running forward due to an open joystick throttle. I had to unmap all the joystick key maps for the 'on-foot' controls.

Hope this helps.