I have several items in it and one of the items is '(None)'.
But what have you coded in a best effort to solve this?
With the combo box set to Limit To List, the field has a value, but you can't see it.
Here are some tips for using Combo Boxes effectively.
But I'd be doing the same thing you should: Experiment like hell.Combo boxes in Access also support the display of multiple columns so you can show more data to make it easier to select the right item.