We have some legacy worksheets that were created in Excel 2003, which are used by LabVIEW-based test automation software. The current LabVIEW software can only handle the legacy .xls format, so we're forced to keep these worksheets as-is for the time being.

We've migrated to Office 2010 and when working with these worksheets, I see this warning:

"The following features in this workbook are not supported by earlier versions of Excel. These features may be lost or degraded when you save this workbook in the currently selected file format. Click Continue to save the workbook anyway. To keep all of your features, click Cancel and then save the file in one of the new file formats."

"Significant loss of functionality"

"One or more cells in this workbook contain data validation rules which refer to values on other worksheets. These data validation rules will not be saved."

When I click 'Find', some cells that do indeed have validation rules are highlighted, but those rules are all on the same worksheet! We're using simple list-based validation, with some cells off to the side containing the valid values (for example, cell B4 has a List with Source "=$D$4:$E$4")

This makes no sense to me whatsoever. One, the workbook was created in Excel 2003, so obviously we couldn't implement a feature that doesn't exist. Secondly, the modifications we're making don't involve changing the validation rules at all. Thirdly, the complaint that Excel is making is incorrect! All of the rules are on the same worksheet as the target.

As if the story wasn't bizarre enough:

I went ahead and saved the worksheet with Excel 2010. I then went to an old computer back in the lab and opened the document with Excel 2003. Guess what - the validations were untouched!

My questions are: is this a legitimate bug in Excel 2010, or is this some exotic error in the legacy .xls worksheet that is confusing the heck out of Excel 2010? Has anyone else observed this issue working in compatibility mode?