One of my Excel worksheets is no longer recognised by Excel 2003. I have
about a dozen worksheets that I use a work [using Excel 2003] and take them
home to work on there [Excel 2007 Beta].

All but one are accessible on both Excel 2003 and Excel 2007. When trying
to use the worksheet on Excel 2003, where it was originally created I get the
message "The file is not in a recognizable format". However, when opening
the file in Excel 2007 Beta the file is still accessible.

Can I get some assistance on what is happening here as I would have thought
if the 11 other files can be accessed by both programs then so should the one
I am having difficulty with.