datagridview with databound checkbox

[gacaccia]

i've got a datagridview that includes a checkbox column. the datagridview is bound to a bindingsource. the underlying table includes a field named "active" of type "bit" (sql server) with a default value of 0 configured at the database level. the checkbox is bound to the "active" field. when running the application, if i create a new record and don't touch the checkbox, i get a error when saving the record that it can't save a null value to the "active" field. all the data binding properties for the datagridview control and checkbox column have been set through VS2005 gui. i've not hand-coded any of it. why am i getting this error and how do i resolve it?

thanks,

glenn