Firmware version 3xxx and upwards on the RNS 510 introduces a new POI system that uses a z-value instead of latitude and longitude.
The map DVD requires a EDB folder for the POI function to work, the older map DVDs will work however the POI function will not operate. The file contains a file called poi.db3 which is the database for the POIs in a SQLlite format. These maps have the new POI database European: 7.1 (7400 and 7404) – out now Australia: 4.0 – due out late 2011
A conversion tool for going to and from z-value to latitude and longitude can be found on the POInspector website here, also on the same site is the tool POInspector used to create your own POI.