Your suggest that MDAC may be the likely culprit is most probably correct or at least along the right path. If you are moving it from the development environment to a production box their are a number of things that you should probably check; are you accessing the same data-store? Perhaps what you are witnessing is the manifestation of different DBMS default behaviours, or perhaps one has been specifically configured / has a different set of integrity rules / something of that nature.

Regards,
Meredith Shaebanyan