Originally Posted by BobBridges

I'm willing to stand corrected ... but I don't think I get it yet. I just selected and uploaded two workbooks, one named x.xls and the other x.xlsx. I selected them both simply by clicking on them in the File-Upload dialog; I didn't type anything additional in the filename text box. When I open the first, it opens normally in my Excel 2010 without complaint. When I click on the second, I get this message: "The file you are trying to open, 'x.xlsx-1.XLS', is in a different format than the one specified by the file extension...." and so on. When I open that one anyway and then offer to save it, it wants to save it as "Copy of x.xlsx-1.xlsx".

I may be mistaken about what MSOfficeForums.com is doing, but it seems to me it's surely doing something that isn't completely correct.