I know it's poor form to repost an unanswered query but I'm desperate so forgive me (just this once).
I have this problem with any browser based form that has a file attachment control on the server.
Whenever I try to download a file from the control on a submitted form it always wants to save it as a file called "CAOT2RO5.aspx". It doesn't matter what file type it is, .doc, .xls. , ppt etc. The correct filename is visible on the InfoPath form. Once the file is downloaded as CAOT2RO5.aspx it can be renamed manually but this is confusing to non-savvy users.
Any ideas?