Combobox bound to not required field tries looking up null value

[Sandra Setz]

Hi,

I have a continuous form with a combobox that gets its values from a
table with no null values. For some reason, whenever I add a new
record in the form, Access tries to look up the current value of the
combobox (null) in the combo, which it of course does not find. I then
get an error message.

I can not leave the record until I select an existing value in the
combobox. But the field the combobox is bound to can contain null
values and is not required. So why do I still need to select an item
from the combo?

Anyone have an idea what I'm doing wrong?

Thanks in advance,
Sandra