1040, new client. Fed return failed efile transmission.  Message says: "Duplicate SSN. A tax return with the same SSN has already been submitted - in other words, it appears you're trying to e-file same return twice...."  There is no duplicate SSN error in the EF center.  There are no duplicate copies of the client.  Searched all 1040's to see if the SSN is duplicate, it is not.  Help please!!