Hi Patrick,
I spend OVER 1 day on this issue.... and belive me I read all stuff based on this issue that are available on this earth :) .
The search "hidden feature" ;) isn't so important at this point.
The important point is the issue with the version. And YES the MOSS is 100% correct configures for browser-based forms and also the Form Services is correct configures.
The InfoPath documents are save on the MOSS (default settings)...Save and opening (of the last version) of this document work fine...
BUT: when you are try to open an older version as the last browser-based forms doesn't work.... please try it self.
Regards,
gicio