See this thread : http://www.mytreg.com/viewtopic.php?f=42&t=7094&start=0 which deals with the same issue I think. I believe that only certain CD's have this data. (Take That : Circus being one of them according to their No. 1 fan Toyboy!). Most ordinary music CD's won't display title and track data. It's not a problem with your head unit.
Discovered something new. Found a cd with mp3 music files and tried it on the RNS 510, and amazingly it plays, and displays the track title and artist as well. Have been busy burning a few more CDs. Absolutely brilliant