Turns out that it was a JBoss problem. I had to remove the driver jar from the deployed EAR file and set a dependency to the module in the JBoss server.
I've manually entered some data into table to see if I could successfully pull data from the table using EclipseLink. Now the convertDataValueToObjectValue method in my Converter throws the following exception:
java.lang.ClassCastException: org.postgresql.geometric.PGpath cannot be cast to org.postgresql.geometric.PGpath
recompile everything with the same version of java? double check dependencies?