This is happening to me now, on a Mac, in an .xls file, so it doesn't seem to be an xlsx file issue or a Windows issue. Did anyone else have any luck figuring it out?

On Wednesday, June 5, 2013 4:22:44 PM UTC-7, witek wrote:
cameron wrote:

I saved as an XLSX file a document that had been an XLS file. This message appears when I open the new XLSX file, and occasionally appears spontaneously while the file is open (or for an unknown reason, at least).



It's funny because Excel suggested that I save the file as XLSX to improve compatibility.







whatever was a valid name in Excel 2003 i.e. sec1 is now a valid cell

reference.



start looking...