@Bernhard: The change to the Palaestina enty is to add the jerusalem hidden resource to it.
This resource is used to make The Temple available only in Jerusalem.

You should copy the descr_regions.txt file from your world/base directory to your world/campaign/barbarian_invasion directory. This is not necessary, but I usually prefer having the files directly in the campaign dir instead of the base folder.

@Legio: interesting, so the game uses the adress somewhere instead of an id.