Your problem is probably due to a problem with the References collection.
References problems can be caused by differences in either the location or
file version of certain files between the machine where the application was
developed, and where it's being run (or the file missing completely from the
target machine). Such differences are common when new software is installed.
On the machine(s) where it's not working, go into the VB Editor (Alt-F11).
Select Tools | References from the menu bar. Examine all of the selected
references.
If any of the selected references have "MISSING:" in front of them, unselect
them, and back out of the dialog. If you really need the reference(s) you
just unselected (you can tell by doing a Compile All Modules), go back in
and reselect them.
If none have "MISSING:", select an additional reference at random, back out
of the dialog, then go back in and unselect the reference you just added. If
that doesn't solve the problem, try to unselect as many of the selected
references as you can (Access may not let you unselect them all), back out
of the dialog, then go back in and reselect the references you just
unselected. (NOTE: write down what the references are before you delete
them, because they'll be in a different order when you go back in)
Nz comes from the VBA library. However, even if there's no problem with the
referenced VBA library, functions in it will be affected if there are
problems with any of the other referenced libraries. This is because looks
in the VBA library last, so that you can override VBA functions with your
own functions.