Cannot Retrieve Binary Data

Hi all ,
i'm following the example at
http://www.postgresql.org/docs/7.4/interactive/jdbc-binary-data.html
trying to retrieve previous stored file (more than 600MB) using the
following code:

Jdbc3ConnectionPool source = new Jdbc3ConnectionPool();
conn =
DriverManager.getConnection("jdbc:postgresql://localhost/backup",
"test", "test");
conn.setAutoCommit(false);
PreparedStatement ps = conn.prepareStatement("SELECT img
FROM images WHERE imgname = ?");
ps.setString(1, "civil.dmg");
ResultSet rs = ps.executeQuery();
if (rs != null) {
while (rs.next()) {
byte[] imgBytes = rs.getBytes(1);
// use the data in some way here
}
rs.close();
}
ps.close();
conn.commit();

during the executeQuery() i got a the following exception

java.sql.SQLException: ERROR: invalid memory alloc request size
2017394403

The Postgres version is 8.0.1 (compiled from source with default
settings ) running on Darwin Kernel Version 7.8.0

Thanks in advance for any help

-patrick