SQL cursor error on AS400

I am running a Java program to retrieve, insert and update data on UDB DB2 on AS/400 using JDBC drivers.  The program is consist of about 18 tasks/batches.  I developed the program in VisualAge for Java 3.5.  I run the same program on both NT and AS/400.  On NT machine, I run test and debug (using AS/400 Toolbox for Java JDBC driver).  On AS/400, I run the program as production (of course, use DB2 native JDBC driver).  Because on AS/400, the program is much fast (about 30 times faster).

When the program try to update a field for a table, I have no problem run on NT (with VAJ), but I got error on AS/400.  The error message is:

        SQL error: Cursor SQLCURSOR000000003 not positioned on locked row.

And this error only occurs when the program run at the first time.  If I run the same code one more time, the error is gone!  But if the program hit another update point, the error will occur again and will gone if I run it second time. 

My code segment looks like this (I only list that I think are related to the SQL operation):

        .........
        stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE, ResultSet.CONCUR_UPDATABLE);
        rs = stmt.executeQuery("select COLUMN1, COLUMN2 from table1 for update");
        .........
       
        rs.updateFloat("COLUMN2", aNumber);
        rs.updateRow();
        ..........

Does anyone have any ideas? 

Thanks.

Weining (Wayne) Xu
ALICO Information Systems & Technology
Wilmington, DE. USA
Phone: +302.594.2846  Fax: +302.594.2215
Email:   weining.xu@aig.com