Trouble with CallableStatement

Hi there,

I'm having trouble getting a CallableStatement to work with the
following function

CREATE OR REPLACE FUNCTION pro_register_cookie_for_user(
prmUserId int8,
prmSecureGuid varchar,
OUT outUsernameHash varchar,
OUT outMaxAge float4)
AS $$
...
$$ LANGUAGE plpgsql;

The function works fine over pgAdmin, so I think the problem lies in
the Java code.

callable = conn.prepareCall("{call pro_register_cookie_for_user(?, ?, ?, ?)}");

callable.setLong(1, playerId);
callable.setString(2, secureGuid);
callable.registerOutParameter(3, Types.VARCHAR);
callable.registerOutParameter(4, Types.FLOAT);

callable.executeQuery();

String usernameHash = callable.getString(3);
float maxAgeF = callable.getFloat(4);

When running this on Java 1.5, pgsql-jdbc 8.1.404 and Postgres 8.1, I
get the following error:

A CallableStatement function was executed and the return was of type
java.sql.Types=12 however type java.sql.Types=0 was registered.
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeWithFlags(AbstractJdbc2Statement.java:380)
at org.postgresql.jdbc2.AbstractJdbc2Statement.executeQuery(AbstractJdbc2Statement.java:250)

Can anyone shed some light on what I'm doing wrong?

Cheers

Michael