I did a research on the internet to hopefully solve the problem. Check if you have any Joystick simulators like vJoy installed. If so you have to disable it or at least reset your bindings to the default settings.
Viewing post in Slender - Dark Woods | ONLINE comments
I think it has to do something with the so called "input dead zone". Quick explanation.. Some Controllers have an idle input of up to 0.3 which causes the player to move without any "known" input.. However that is a bit harder to fix because I am not able to let the users individually customize this dead zone. I am trying to do my best