Brian,
I don't use MM, so I have no clue how the BO's are set up or how you use the BO's as a DataSource for your Combo, but maybe if I tell you what we do in a similar situation, it might help.
We use many Combo's on a single form, and many use the same DataTable as their DataSource. What we do is bind to a copy of the DataTable and that solves the problem ... just use MyTable.Copy(). I don't know if it'll help you or not, but it might get you thinking in the right direction.
~~Bonnie