images display fine...until I generate a page's PDF

I have an app which has lots of images (photos, logos, signatures, etc.) and the all seem to display fine on all my reports, forms and Pages.

BUT when I click the "PDF" button on a page, the resultant PDF file shows a blank box. Printing the Page is fine and the image gets printed out, so the problem seems to be with the PDF button.

Any ideas what I'm doing wrong? What I'd like to do is be able to click "PDF", create the PDF file and then email it to a client. Nothing fancy I would think, but I can't get it to completely work.