Updating a table through a select query: text fields update, but not yes/no fields

[Carbontrader]

I know this is a fundamental question, but I'm stuck.

tblStaff has normal personal information about project staff, including several Yes/No fields. My data entry form has the following query as its data source:

SELECT tblStaff.*, tblStaff.LastName
FROM tblStaff


ORDER BY tblStaff.LastName;

I can update any of the text or numeric fields via the form, but not the Yes/No fields that are displayed as check boxes or option buttons. What am I doing wrong?

[Carbontrader]

Solved: the Check Box control had been set to Triple State. Removing that solves the problem, but I'm not completely sure why.

[Micron]

When you deselected the checkbox was it blue or white? Blue is neither yes or no (may be null, but I've never tested that) and to edit such a field requires it to be either y or n. It can't be neither (blue) once it has been one or the other. By removing the triple state option, you've forced it to be one or the other. That's the only thing I can think of, but I don't use them too much so maybe someone will correct me.