What version of FileMaker was installed on your computer before you tried installing the upgrade?
Installation problems (and I think this issue would be considered such) are handled for free by FileMaker Tech support so you might call tech support for assistance with this.
I have version v.02 installed right now.
Do you still have the installer for 12v02? If so, you might try re-installing it and then try the upgrade again. (And if you don't have the original installer--something you should always hang onto, you can get a new download for tech support if you registered your original purchase so that you can prove to them that you paid for the product.)