I've been at this for several days, and have had almost no luck in even the smallest degree.  I've been trying to generate XLSX files for a web project I am working on, however I can't even properly modify the example files without Excel 08 (for Mac) stating they are invalid.

For example, I take one of the example files that is in a format like such:

<foo><bar/></foo>

And attempt to clean it up so that I can properly look at and analyze it.  I format it like such:

<foo>
        <bar/>
</foo>

Then zip it back up and go to open it, and Excel claims it's been damaged.  I can't even change a worksheet's *name* without it saying that it's broken.  However, OpenOffice.Org and Numbers can both open the file fine.

Any help would be greatly appreciated in this matter.

Eric M.