Please deselect the option that you never selected

I went past this screen twice while finalizing a flight with Northwest Airlines.

 

I never touched the Frequent Flyer Program section, so I was a bit thrown when it told me I had selected a loyalty program and needed to deselect the name to continue. Thrown further because there's no way to deselect the name shown in the pop-up menu.

 

The should-have-been-selected-by-default radio button two inches to the left of "No Frequent Flyer Program" did the trick, natch'.

Done