By chance, is the field to which the combobox is bound is a text field and
has a Format property setting for the field in the table? If yes, this is a
bug that has been reported by many ACCESS users during past weeks. It
apparently is a bug in Office 2003 SP3, which was released by
MS some weeks ago. MS is aware of the bug and is working on how to fix it.
In the meantime, the "complete workaround" is to remove the Format
property's value from the field's properties in the table's design view.
Otherwise, concatenating the field's value with an empty string also seems
to "overcome" the problem.

Signature
Ken Snell
<MS ACCESS MVP>
> An application I wrote 3 years ago no longer works after applying SP3 to
> Office 2003. Unbound combo boxes used to display 2 columns but now the
[quoted text clipped - 3 lines]
> column
> drop-downs. Solution?
Ken Snell (MVP) - 28 Dec 2007 01:27 GMT
"Combo box controls and list box controls display no value or
incorrect values in Access 2003 after you install Office 2003 Service
Pack 3." And a few more problems SP3 introduced.
Description of the Access 2003 post-Service Pack 3 hotfix package:
December 18, 2007 - 945674
http://support.microsoft.com/kb/945674

Signature
Ken Snell
<MS ACCESS MVP>
> By chance, is the field to which the combobox is bound is a text field and
> has a Format property setting for the field in the table? If yes, this is
[quoted text clipped - 15 lines]
>> column
>> drop-downs. Solution?