I think I worked it out.
 
It's just a matter of making the jndi name global.
 
It seems that JBoss does not allow me to use the mysql
repository name as a local "java:" name.
 
I made it global and everything went smoothly!
 
Now I am just wondering whether there is a chance
to make it local in someway....
 
Is it possible? Is it a JBoss 4.2.2 BUG?
 
I post the old .xml files again:
 
(In the current version I just disabled the local namespace setting: <use-java-context>false</use-java-context>)
 
<datasources>
 <local-tx-datasource>

  <jndi-name>jdbc/MySQLDB</jndi-name>
  <connection-url>jdbc:mysql:///brms-db</connection-url>
  <driver-class>com.mysql.jdbc.Driver </driver-class>
  <user-name>drools</user-name>
  <password>drools</password>
  <min-pool-size>5</min-pool-size>
  
  <max-pool-size>20</max-pool-size>
  
  <idle-timeout-minutes>5</idle-timeout-minutes>

  <exception-sorter-class-name>
  com.mysql.jdbc.integration.jboss.ExtendedMysqlExceptionSorter
  </exception-sorter-class-name>
  
  <valid-connection-checker-class-name>
  com.mysql.jdbc.integration.jboss.MysqlValidConnectionChecker
  </valid-connection-checker-class-name>
  
 </local-tx-datasource>
</datasources>
 
I've got the following persistence manager set-up in <jboss_home>\bin\repository.xml:
 
 <PersistenceManager class="org.apache.jackrabbit.core.persistence.db.JNDIDatabasePersistenceManager">
  <param name="dataSourceLocation" value="java:jdbc/MySQLDB"/>
  <param name="schema" value="mysql"/>
  <param name="schemaObjectPrefix" value="${wsp.name}_"/>
  <param name="externalBLOBs" value="false" />  
 </PersistenceManager>
 
Hope u can help with this.....
 
Massi