Hi Joe,
Is it just a coincidence that this other question was asked within an hour or two of you asking yours?
http://www.wikitree.com/g2g/3965/gedcom-backup-problem
I'd answer you the same way:
I assume you've received the e-mail that says your file is ready for download, and you're clicking on the link? Have you tried right-clicking the link with your mouse, and selecting "save link as"?