Why am I getting this error message in my DITA Topic? "Element (concept) is undefined"

Frame 11

DITA 1.2

I was finally able to create a DITA topic (rather than a reference, concept, or task). However, when I try to insert a task, concept, or reference element after the prolog, I get the following error message:

     Element (concept [or task, or reference]) is undefined.

My Topic general rule looks like this:

title, titlealts?, abstract?, prolog>, body?, related links?, (topic | concept | task | reference)*

in the topic.eddmod.fm and has been imported into topic.edd.fm, and topictemplate.fm in addition to concept.edd.fm, reference.edd.fm and a whole boatload of others and their related templates.

Doesn't my general rule "define" concept, task, and reference? If not, what am I missing?

Thanks in advance all you helpful people.

Marsha