calling java stored functions through jdbc gives errors.

The following simple query I send to the server using JDBC:

"SELECT uw_ping()"

When the stored function uw_ping() is written in 'plpgsql' everything
works fine. But when the uw_ping() is written in java and linked in
using PL/java it gives the following error message:

org.postgresql.util.PSQLException: An I/O error occured while sending
to the backend.

Executing the same query using pgadmin III gives no problems. Anyone
any idea what the problem is?

Best regards,

Alex Stienstra.