jdbc fastpath error & Z error (URGENT NEED!!!)

Hy, Postgresql community!

I'm using:
Linux RedHat6.2,
PostgreSql6.5.3+jdbc6.5-1.2,
jdk1.2.2
(AND I CAN'T CHANGE THIS "KIT")

I've got the below java program and when I type:
# javac PicImmitter.java , it's all ok.
But my problem occours when I run:
#java PicImmitter
..........and this is the error output:

"FastPath protocol error: Z
 at postgresql.fastpath.Fastpath.fastpath(Fastpath.java:159)
 at postgresql.fastpath.Fastpath.fastpath(Fastpath.java:188)
 at postgresql.fastpath.Fastpath.getInteger(Fastpath.java:200)
 at
postgresql.largeobject.LargeObjectManager.create(LargeObjectManager.java:162
)
 at postgresql.jdbc2.PreparedStatement.setBytes(PreparedStatement.java:298)
 at ProvaPicIn.<init>(ProvaPicIn.java:48)
 at ProvaPicIn.main(ProvaPicIn.java:11) "

What can I do, exactly? My Program is:

import java.awt.*;
import java.io.*;
import java.io.FileInputStream;
import java.sql.*;
import postgresql.largeobject.*;
import java.io.IOException;

public class PicImmitter extends Frame{
 public static void main(String args[])
 {
     PicImmitter app = new PicImmitter();
    System.exit(0);
 }

 public PicImmitter()
  try{
    Class.forName("postgresql.Driver");
    Connection conn=DriverManager.getConnection("jdbc:postgresql:best",
                                  "Myuser","Mypwd");
    FileInputStream fis = new FileInputStream("015.jpg");
    int nBytes = fis.available();
    byte [] buff= new byte[nBytes];
    int bytesPhoto = fis.read(buff,0,nBytes);
    String photo = new String(buff);

    conn.setAutoCommit(false);
    PreparedStatement ps = conn.prepareStatement("update players set
                                         image = ? where playercode=? ");
    ps.setBytes(1,photo.getBytes());
    ps.setInt(2,15);
    ps.executeUpdate();

    fis.close();
    ps.close();
    conn.setAutoCommit(true);
    conn.close();
  }catch(Exception ex){
      ex.printStackTrace();
  }
 }
}

THANK'S A LOT
MARCO FROM ITALY