When I save one of my workbooks I frequently lose some of the formatting. Usually it is the last that has been entered. The workbook is only about 500k in size.

I am using the old Excel 97-2004 spreadsheet format with Excel 11 on a Macbook Air/Lion with bags of spare available ram. Could it be due to the old format and if so how can I upgrade it please?

Many thanks in advance.

Paul