Unreadable Content error

[dta1984]

I get an error message saying Excel found unreadable content, would you like to recover...... when i open my workbook. I click OK and all is well, and the workbook opens as normal. Just would like to get to the root of the problem to figure out what is causing this error.

After some searching around some have listed that Named Ranges could cause this. My workbook has 100s of rows with named ranges in the formula. Most of the workbook contains sumproduct formulas, and vlookups. Any other ideas or ways to find out where the error is? There are no vba functions or macros in this workbook.