For the last several versions, each version of PPT has gotten fussier about what it will and won't eat. Some little thing that earlier versions might have just ignored and gone on about their business can make later versions throw up their hands and run screaming into the night.
One trick is to "round-trip" the file to HTML and back from a version of PPT that supports it. That can weed out some of the little bits of cruft that make PPT 2013 go uncooperative.
In PPT 2010, you'll need to use VBA to do this, since the Save As HTML feature has been removed. You can find the code on one of my FAQ pages, here:
Ignore the reference at the bottom to PPT2HTML ... it's a useful add-in but won't help with this problem.