I'm printing a document which has a bunch of PNG images in the source. All the images have been created in the same way (with Photoshop) and saved to the same location.

When I create the PDF all but one of the images shows up, and the log file shows the following warning:

Wed Apr 1 18:24:38 2009: http://se-local/sites/all/files/s2-3.png: warning: Could not load PNG file

The file definitely exists on that path and copying & pasting the full URL into a web browser displays the image. All the other images in the same location show up just fine. What could the problem be?

Perhaps Prince does not like the format for some reason. Is the image publicly available for testing?

Hmmm, seems to be a problem with the file - maybe corrupted somehow. Can view it in the browser and image preview but Photoshop refuses to open it.