environment_server doesn't subscribe to collision_map

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I want to generate a collision map from kinect's pointcloud and use this info to do a collision-free arm navigation. so i write a node to receive pointcloud from kinect and publish collison_map with the topic "collision_map_occ". i think i've done this correctly because i can see these collision map green boxes in rviz. but it seems that environment_server doesn't subscribe to the collision_map topic. i'm sure that the param use_collision_map is set to true. does anybody know why?

besides, according to this tutorial, "If the use_collision_map parameter for the environment_server is set to true there must be a supplier of the CollisionMap or the environment_server will not start", but after i stop the collision_map publisher, the environment_server can still start successfully.

btw, i'm using Fuerte on Ubuntu12.04