In the File - Print options, you should see a checkbox, "Frame Slides". Make sure that this one is unchecked.
Also, go to View - Master - Slide Master, select all objects using Command+A and see if there is a hidden border or slide shadow that is being used somewhere on the template. If it is, deselect everything and delete the offending shape or border.
Beyond this, I'm not sure what is causing the problem, but these are the two most likely places in PowerPoint you might want to check first.
Hope this helps.
Jeff