Hello,
I suppose it could be the exe - one requirement is that _exclsub.llb and _wordsub.llb must be added as support files when building an application or a dynamic link library with the application builder. Those libraries can be found in the directory:
C:\Program Files\National Instruments\LabVIEW 7.1\vi.lib\addons\_office
If you haven't already, try including those as support files when you build the exe, and try it on your machine that only has the LabVIEW Runtime Engine again.
Best Regards,
JLS