IT sure sounds like this is caused by trunking, or a hub. UT will display multiple MACs on the same port if there is a hub, or other port multiplier device hanging off the port, and the port is not trunking. If, however, the port has a CDP neighbor, and that neighbor shows up on the Topology Map, then UT will ignore that port (i.e. not show any end hosts).
If you are using Campus Manager 5.0 or higher, you could have enabled end host acquisition on trunk ports in UT. If this is enabled for that port, then UT will show end hosts even if trunking is enabled.
