I followed this this guys (bjornvil) advise from a forum called giantbom:
"I downloaded Xpadder, and only used it to map the analog sticks to the wasd keys (left stick) and the mouse (right stick), leaving all the buttons alone, and voila! problem solved! Needed to do a little tweaking to the sensitivity of the right stick to get the turn rate right, but now it plays like a dream and I am loving it!
...and the controls with the 360 pad feels so much better now. Highly recommended for gamepad users
As a side note: Normally i donīt prefer gamepads over mouse+keyboard, but in this game i couldnīt get along with the m+k controls.