"Invalid argument" error message when trying to use a combo box

I have an Access 2000 backend database on a Windows 2000
Small Business server. Front end is an MDE database. I
have a subform with a combo box that works fine on the
front end when working on the server, however when working
in the front end on a Windows XP computer the combo box
gives me the "invalid argument" error and there are no
options in the drop down box to select from. I have other
combo boxes on the same subform that work fine. Any
thoughts? Thanks.