Saving as binary workbook

I have a big workbook with lots of calculations, I saved it as a binary workbook but when I open it it gives me an error "excel found unreadable content, do want to recover the content." Anybody have any reason why this happens, and should I even use binary workbooks.

Thanks
Jeremy

I don't know why that's happened, but wokbooks can get corrupted. The answer to your question is absolutely yes; binary workbooks are smaller, faster and more efficient; their only real limitation is compatibility, they con't conform to the xml standard, but if you are only ever using them in a recent version of excel, this is unlikely to be an issue