I am using excel 2007, and I am having a problem with saving a file. When I save the file the compatibility checker opens and tells me I have a minor loss of fidelity. The exact message is:

"Some of the formulas in this workbook are linked to other workbooks that are closed. When these formulas are recalculated in earlier versions of Excel without opening the linked workbooks, characters beyond the 255-charachter limit cannot be returned.
Location: Defined Names"

To try and track this down I first went to defined names, I'm not using any and the name manager doesn't show any. I then made a copy of the file, and deleted the tabs one at a time to try and see if that would do it. I have deleted all the tabs in the original file, and created a single new blank tab. I have confirmed that there are no defined names in the names manager, and I am still getting the message telling me there are 22 occurrences of this error.

TL;DR
Error about defined names, but there aren't any in the workbook. Any suggestions what might be causing this and how to fix it?