Betsy,

It is possible that you are seeing this problem intermittently because some
of your client machines may already have those DLL's installed by another
application that also uses those libraries.  As Tony suggested, I would also
recommend careful version control of the DLL's.  Otherwise, copying the
files to ..\Windows\system for all clients should, as suggested, be a safe
solution.  I would look at the version of the DLL's on a machine that you
did not have to manually copy, and make sure they are the same version you
are using.

Good luck,

Greg Heis