Hello Brian,
I ran into almost the exact scenario as you using integer key types. If I created the combobox on a form it worked fine, put it in a class and it choked. I went over a variety of tests and the thing that finally worked was to re-establish the control source. Ex: in the init() of the combobox
This.RowSourceType = 6
This.RowSource = a.ingred,ingred_id
lcCurrentSource = This.ControlSource
This.ControlSource = ""
This.ControlSource = lcCurrentSource
For some reason, by clearing then re-establishing the control source it works. Hope this helps you out.