Troubleshoot MS Access Error Message

The following error message pops up each time I select the next record in my form:
"The value you entered isn't valid for this field. For example you may have entered text in a numeric field or a number that is larger than the FieldSize setting" The form feeds data to a table with only two number fields both set to FieldSize "Long Interger" All other fields are either Text, Memo, or Date fields. The data entered in the number fields are intergers. Why is the error message appearing each time I select a new record?