Ray as terrain follow?

I want to be able to move an object freely over a terrain, for example a fps without the ability to jump. However, when adding a Ray Logic Brick, the Motion Actuator doesn’t respond, that is, whenever the ray detects the ground. In the following screen:

http://kawzon.se/forum/upload/ray_gravity.jpg

I have an extruded plane with the boolean property “ground” and a ray logic bring looking for objects with this property. As soon as the plane is detected (when pressing down D to move the cube to the right) the cube sticks to the defined height, but will not be able to move again.

Any ideas on why this is happening? I’ve tried different settings, but can’t figure this one out. It’s probably something really simple… :rolleyes:

Blend: http://kawzon.se/forum/upload/ray_terrain_follow.blend