Save As Image fails with PDF files

Using Acrobat X Pro, version 10.1.7. After the most recent update, I can no longer crop a PDF file and save it in any image format. The options are there, but when I select File > Save As > Image > PNG (or JPG or any other image format) and enter the filename/location, no new file is created.

This is about to become an emergency, since a big annual production project uses images from PDF files as illustrations in other documents.

Any ideas?

Elisa