Upon opening my workbook I receive the error:
Excel found unreadable content in 'MyWorkbook.xlsm'. Do you want to recover the contents of this workbook? If you trust the source of this workbook, click Yes.
So I click yes and my workbook loads just fine. Or appears to load just fine from what I can tell. Then I get the message:
Excel was able to open the file by reparing or removing the unreadable content. Repaired Records: String properties from /xl/sharedStrings.xml part (Strings). Click to view log file listing repairs: C:\Users\MyUserFolder\AppData\Local\Temp\error120480_01.xml
So I open up that XML file and it says:

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Any idea what this is? At this point, I have to revert to a backup copy of the workbook because even if I save it as another name, I still receive this error.

Thanks for your help!