The Make Delphi action should only update the product version if 'Update the Product version' is checked on the Versions tab.
http://www.visualbuild.com/Manual/delphversiontab.htm
If that is not the case, please ZIP and send or post:
1) The info from Help | About | Install Info
2) The .bld file
3) A build log file
4) The Delphi project files (no source code files)
Thanks.