I had the same problem with x52. Try to disable the 2 rotating wheels on the throttle. In My case they where configured by default by xp as vertical and horizontal trim. This caused trouble with autopilot and the trim wheel worked very hard . Just go in the xp setup then in joystick config and move the 2 wheels. If they are associated to a trim control disable it and choose do nothing from the dropdown menu. Hope this Can be of some help