You are seeing a PostgreSQL database error. OpenERP began an insert transaction which then failed. It ignored that failure and continued trying to use the SAME TRANSACTION to run another insert. PostgreSQL threw the exception on the second, correctly formed insert because OpenERP tried using a broken transaction to do additional work. Correctly, PostgreSQL does not allow this.

I think it is certain that your file sample.partner.csv contains illegal Comma Separated Value (CSV) formatting that OpenERP fails to notice. (A bug! You should report it.)

Solution : Divide and conquer! Try removing rows and columns until you get a succesfull load. That will help you pin point the culprit.