summary option missing for .xls files

[rowland]

I often use the “summary” options available under the file properties, to add comments to MS excel documents, the problem I have is that sometimes when I go in to properties this option is missing and I am only given the option for general and security (the custom option is missing also), but eventually with all the problematic files, as if my magic, and without me making any alternations, the option returns after an indeterminable amount of time.

I am just wondering if anyone knows why this option would go missing.
All the files I have had the problem with are .xls files created in ms Excel 2003