Locking

I'm running into a problem where an "AccessShareLock" is not being
released after a select statement unless a connection is closed. This
is leading me to a deadlock issue with deletes. I'm using JDBC to
interact with the database. I'm using postgresQL 8.0. I was under
the impression that resources (does this include locks) are released
when the prepared statement is closed. The code snippet looks like the
following (though it does more prosessing then in this example. Is
there something that I'm missing to release the locks?

String sql = "select * from testtable";

PreparedStatement prest = con.prepareStatement(sql);

ResultSet rs = prest.executeQuery();

rs.next();

rs.close();

prest.close();

con.close();