Experimenting with the builder again today and created a fighter and tried to take elven arcanum for being able to access the elven arcane ranger line. The description states that elven arcanum can be taken at level 1 with no limit or pre-req for being able to take it. As such it remains greyed out. I am assuming this to be an error since an elf can become and elven arcane user without having the ability to cast spells.

If I cam wrong I would like to know as well. Any information regarding this would be appreciated.