Environment
- JBoss Portal 2.6.1 bundled with JBoss AS 4.2.1 downloaded from downloads.sourceforge.net
- Oracle Database 10g Express Edition Release 10.2.0.1.0
- ojdbc14.jar (Oracle JDBC Driver version - "10.2.0.3.0")
- Windows XP SP2 and Fedora 4
- jdk 1.5.0_11-b03

Problem
If I modify twice user parameters through the UserPortlet I obtain a unique constraint violated exception:

ERROR [AbstractFlushingEventListener] Could not synchronize database state with session
org.hibernate.exception.ConstraintViolationException: Could not execute JDBC batch update
 at org.hibernate.exception.SQLStateConverter.convert(SQLStateConverter.java:71)
 at org.hibernate.exception.JDBCExceptionHelper.convert(JDBCExceptionHelper.java:43)
 at org.hibernate.jdbc.AbstractBatcher.executeBatch(AbstractBatcher.java:253)
 at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:237)
 at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:144)
...

Steps
1. login
2. User portlet >> edit your profile
3. modify some properties
4. Save changes
5. logout
6. repeat from step 1

How can I solve this problem?
Thank you in advance.

Regards
Angelo