The only missing references I see are those to missing buttons and
controls. That is, when the activeX controls do not get loaded, the
subroutines envolved with them complain that no such items exist.

We may have found a kludge to work around this, but I'd still be
interested in knowing why it's happening. When I was able to actually
work with two of the machines in question, I resaved the program on
the machine  it worked on in Excel 2003 and then moved that copy to the
machine it didn't work on. That moved copy worked. We'll need to try
it on the other machines it's not working on to be sure this fixes
(but does not explain) the problem.