Cannot select less than full size when inserting photos

I cannot select any option other than full size when inserting a photo into a page. I have recently upgraded to 7.1 and this did work fine before. This is true whether the uploaded graphics are new or were uploaded prior to the upgrade. I can see the thumbnail in the media library.

All other options when inserting graphics are selectable. A full size photo does get inserted, but the ones I need to insert are too big to be full size.