Hi David,

Use tags

 < pre >
  code 
 < /pre >

for more readability on UT message.

If you can,
Use COMMAND, not PROCEDURE, on Menu designer for single line command.

The problem is expanded too much.
An operation exists sure that generates the error.

You must cut the flow of the code, in order to find the operation that cause your problem (a DEBUGGER inner, in these cases it is not much profit, it would serve an external DEBUGGER)

1. You insert of the RETURN in several points
(also within to message_question,auto_archive,insert_layer).

Example:

DO CASE
CASE THISFORM.pgfCREdetails.ACTIVEPAGE=1
	* 1° insert RETURN 
	IF THISFORM.message_question('Insert a new rent layer?')#6
		RETURN
	ENDIF
        * 2° if not error remove 1° and insert RETURN here
	IF THISFORM.layercount_val=5 &&archive oldest +insert new layer 
		THISFORM.auto_archive
	ELSE && insert new layer 
		THISFORM.insert_layer
	ENDIF
	* ....
ENDCASE

I am not in a position to writing more.

Fabio