For some reason that I just can't explain, a text box on a form associated
with a single primary key field behaves unexpectedly when I do a
filter-by-form.  Instead of listing all of the records from the source table
as choices in combo box mode, I only see "Is Null" and "Is Not Null" as
choices.

I have an older form from another database that behaves as I hoped this one
would, yet there seems to be no property differences between the two text
boxes.  Can anybody explain what I'm missing please?  Having "Is Null" and
"Is Not Null" as filter-by-form choices just doesn't cut it!

Thanks!!!