but when I try to click on the control and choose a record, the control seems to not display anything. If I choose using keystrokes, it displays the record.

Is this a plain vanilla base class combo box or is it a subclass? Is there any code in any of the methods?

Also, I would want it that field2 would be displayed on the control, but field1 would be the first column on the control.

You can't do that. The DisplayValue of a combo box (the value that is displayed in the combo when the combo is "closed") is always taken from column #1 of its internal list.