And have you tried printing directly from an image editing program (or from Internet Explorer?)

It could be a print head problem (which you would diagnose if it does this when you try to print text or anything else.) Also, try looking at the picture in IE -- IE should actually be able to open it up and view it.

That will tell you which device is causing the problem. If you can print from IE with no shadow and look and see no shadow, then the problem is MS Publisher. Reinstall MS Publisher.