i upgrade mysql-3.23.47 to mysql-4.0.15,while i restart web server once,only select one board post list or select message list,throw some exception below,but refresh the page,the error can not be shown agin,why???i try to change org.gjt.mm.mysql.Driver to com.mysql.jdbc.Driver is either.Who can tell and help me?

Can't set field:reply:Operation not allowed after ResultSet closed
java.sql.SQLException: Operation not allowed after ResultSet closed
at com.mysql.jdbc.ResultSet.checkClosed(ResultSet.jav a:3562)
at com.mysql.jdbc.ResultSet.checkRowPos(ResultSet.jav a:3544)
at com.mysql.jdbc.ResultSet.getString(ResultSet.java: 1732)
at com.mysql.jdbc.ResultSet.getInt(ResultSet.java:124 6)
at com.xxx.dbo.DBObject.instanciateFromDB(DBObject.ja va:237)
at com.xxx.dbo.DBObject.getdbObjects(DBObject.java:14 6)
at com.xxx.dbo.DBObject.getdbObjects(DBObject.java:16 4