Hi Gary,
I ran a stack of 10 images using your AIJ_Prefs file and I get a valid relative flux for each image (see below). I noticed that auto comp stars is not turned on. Are you manually selecting a comp star? I selected one manually for my run. Other than that, I made no changes to your set up.
Or is this only happening when running from a Macro? If so, can you check outside the macro environment to see if the problem still shows when you run AIJ interactively?
Karen