Forms :: Subform Creates Duplicate Records

I have a form that uses Table A as a record source and has a subform that uses Table B as a record source. There is a one to many relationship between Table A (one) and Table B (many).The user opens the form to a set record, then uses the subform to create a new record in Table B.

This works perfectly and I can do everything I want. But sometimes the subform creates a blank entry in Table B before I enter any data. Then, once I start entering data, it creates another record in which it stores the data that I am entering.The result is two records: One that only has the date of the record's creation (I set that to be automatic upon creating a new record) and the primary key that links Table B to Table A. A second one is the "true" record, the one which stores all of the data that I am entering.

It won't happen for 10 records or something and there is no apparent pattern. In case it makes a difference, the form is set to open as the subform as the focus.