New Post: Excel 2013 - 2010 compatibility

Hello
I reproduced.

1) Create an Excel file "Book1.xlsx" with Excel 2013 / Windows8.1.
2) Execute below with Excel 2010 / Windows 8:

            XLWorkbook xl = new XLWorkbook(@"c:\AnyPath\Book1.xlsx");
            xl.Save();

3) Open Book1.xlsx with Excel 2010 / Windows 8.
4) Input any string and save.
5) Open Book1.xlsx with Excel 2010 , "unreadable content" error occured.
6) Execute 2) again, " 'x' was an undeclared namespace" error occured.

ClosedXML version is 0.75.0.
I hope this helps to fix the problem.