Upgrading jdbc

Hello!

I'm trying to upgrade to the current jdbc.
I tried both jdbc3 and jdbc4.

Until now we've been using pg74.215.jdbc3.jar.
The code is using methods that need a ResultSet with a Type different than
TYPE_FORWARD_ONLY. In the 7.4-version this seems to be standard.

For the new one I need to do:
PreparedStatement stmnt =
connection.prepareStatement(JDBCEscSeq.convertEscSeq(sqlStmnt, objs),
java.sql.ResultSet.TYPE_SCROLL_INSENSITIVE,
java.sql.ResultSet.CONCUR_READ_ONLY);
for the code to function as before.

So far this works. Unfortunately the execution of some statements is
extremly slow.
I identified "org.postgresql.core.v3.QueryExecutorImpl.receiveFields()" as the
point where the time is spent.

I'm using JDK 1.6.

Are there any hints I'm missing, any settings I need to set?

Thanks for advise, H. Wurth