Can't add attribute to 0-length text

I have a CFREPORT Template that has been running fine for months. This report has 8 layered controls (Color coded page tabs for a Table of Contents). Yesterday I added 2 new Calculated Fields and added 2 layers to the 8 making ten layers. Each layer has its own "Print When" clause etc etc. Ever since I have been getting the error message in the title of this thread.

Is there some kind of clue or secret code to help figure out what is going on here? I have no 0 length text at least that I can see. How can I pinpoint which control or field may be causing the problem?