To the best of my knowledge the error message, "References to Additional 3d geometry may not be made; please select again", occurs when you try to add references to a feature that has been copied or (possibly) in a feature group. You will have to break the dependence before you can add dimensioning or orientational references to this feature. In the past I deleted the copied feature, but you might try selecting the copied feature, right clicking and choosing "make the section independent". It is available in Wildfire 1.0, and I assume was a program feature carried on into future versions. If you need the dependence, the first option means you will need to know how the feature was copied (mirrored, translated) and what the copy references are so that you can repeat the copy once you've added the new references. The second option just means that you've lost the dependency, but you can add relations to recapture dimensional dependency.

hope this helps.