Sorry, I was editing my original post to clarify what led to the flameout. Here are the added details, again:
"ETA: To clarify, dropping .rom files onto the window crashes out the application instantly. Dropping onto the .app icon in the dock loads the .rom without issue. For whatever reason, I figured dropping onto the window would also work ... guess not. Should it? If not, can the window not serve as a drop target to prevent frustration?"
Hmmmm! Libsdl is handling the window, I guess I need to ask in the forums.