SBS2003 and Internal DNS name resolution

Hi, I'm administrating a SBS2003-R2 Premium based network and have noticed that some of the domain computers create sessions with the server using their IP addresses instead of their registered names. I'm not experiencing any problems with the network but this is a niggle and I'm concerned that it may be pointing to an Internal DNS problem that I'm unaware of. Has anyone experienced this and found a resolution? Any info will be greately appreciated.