Just a thought ... could it be that you still have the free samples of the book that you might have downloaded before buying the book? Those aren't deleted automatically when you buy the full book and can make it look, at a glance, like you have two copies of the same title.
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ROBERT J. SAWYER, Science Fiction Writer
Author FLASHFORWARD, basis for the TV series
http://sfwriter.com *
sawyer@sfwriter.com