Whoever is responsible for the error messages found in Oracle's TopLink product is one sick individual.
TopLink Essential is a Java EE 5 persistence provider. It was contributed by Oracle to Glassfish and serves as the reference implementation for JPA. If you're a Glassfish user, do yourself a favor and setup another JPA provider.
Following these instructions, getting Apache OpenJPA to run inside Glassfish takes about 2 minutes. You can also use Hibernate if you so wish by following these instructions.