Sometimes when a text frame or image with a transparent background, e.g. in png format, is placed on top of another image acting as a background, it prints out showing a faint discolouration of the background image so that you can see where the borders of the item on the top layer are. This is not visible on the screen, however. Any ideas what causes this? I remember having the same problem a few years ago and can't remember how I worked around it.
It's a bit hard to say wthout seeing it, it might by YDB Syndrome, the plague that was first described, documented and named by eminent and white-coated InDesign specialist Claudia McCue here. Another fix for that is to try making the background colour process or RGB, not a Pantone Spot Colour. If that doesn't work you could try posting a screenshot on this forum, use the camera tool on the web interface to upload a previously saved screenshot.
Actually, what causes this is the fact that an image with a transparent background invokes transparency and depending upon how you print, printer driver, printer model, etc. you may be encountering flattening artifacts. See Claudia McCue's article on this at http://indesignsecrets.com/eliminating-ydb-yucky-discolored-box-syndrome.php.