How can something be duplicate content of itself?

[BetAmerica]

Just got the new crawl report, and I have a recurring issue that comes back around every month or so, which is that a bunch of pages are reported as duplicate content for themselves. Literally the same URL:

http://awesomewidgetworld.com/promotions.shtml

is reporting that

http://awesomewidgetworld.com/promotions.shtml

is both a duplicate title, and duplicate content.  Well, I would hope so! It's the same URL!

Is this a crawl error? Is it a site error? Has anyone seen this before? Do I need to give more information?

P.S. awesomewidgetworld is not the actual site name.

[matbennett]

That doesn't sound right at all.  I'd email help@seomoz.org with that one to be honest.

[BetAmerica]

Did that, thanks! I'll report back what they told me so we can all learn.