Using Japanese vs. US version of Access

[davidz]

I have been asked to help maintain a small Access application that was
developed in our US office using the US version of Access, but it is to
be used by our office in Japan, which has a Japanese version.
Unfortunately, this has turned into a "joint maintenance" arrangement
in which I do most of the work, but the Japanese users are able to make
minor modifications of their own. I then have to get their most
current copy before I can make further changes. We ran into a problem
the other day when they send us a copy of the most recent version that
they were using (one which had some changes they had made), and I
discovered that I was unable to open that version on my end. This
leads me to be concerned that altering an .mdb with their version may
do something to it that my version cannot deal with. Has anybody come
across anything like this before? (My own preference is for the
Japanese users to not make any modifications of their own, but I have
not prevailed in this.) Thank you.