Are they running Windows Vista? I have read somewhere that Vista makes a
"copy" (of a subset?) of the registry for use by install programs, to keep
them from overwriting areas or keys that they are not supposed to. If the
application is then given a different "copy" or subset of the normal
registry to work with at run-time, then maybe it can't fetch the value that
it is looking for.

Just a wild guess.
--
Regards,
Bill Renaud