Duplicate class/entity mapping com.xpn.xwiki.doc.XWikiDocument (from: xwiki.mssql.hbm.xml)

Dear Readers,

After having a fine working version of the XWiki Enterprize version 1.8, I'm having trouble installing version 1.9. We use MS SQL Server and had our share of problems running XWiki on it, but they were all solvable. This time we need help....

While mapping the file xwiki.mssql.hbm.xml hibernate comes with the following error:

org.hibernate.DuplicateMappingException: Duplicate class/entity mapping com.xpn.xwiki.doc.XWikiDocument
at org.hibernate.cfg.Mappings.addClass(Mappings.java:118)
at org.hibernate.cfg.HbmBinder.bindRoot(HbmBinder.java:145)
at org.hibernate.cfg.Configuration.add(Configuration.java:675)
at org.hibernate.cfg.Configuration.addInputStream(Configuration.java:510)
at org.hibernate.cfg.Configuration.addResource(Configuration.java:572)
at org.hibernate.cfg.Configuration.parseMappingElement(Configuration.java:1593)
at org.hibernate.cfg.Configuration.parseSessionFactory(Configuration.java:1561)
at org.hibernate.cfg.Configuration.doConfigure(Configuration.java:1540)
at org.hibernate.cfg.Configuration.doConfigure(Configuration.java:1514)
at org.hibernate.cfg.Configuration.configure(Configuration.java:1434)
at com.xpn.xwiki.store.XWikiHiber......

The hibernate settings we use:
<!-- MSSQL Configuration -->
<property name="connection.url">jdbc:jtds:sqlserver://localhost:3306/xwiki;tds=8.0;lastupdatecount=true</property>
<property name="connection.username">xxx</property>
<property name="connection.password">yyy</property>
<property name="connection.driver_class">net.sourceforge.jtds.jdbc.Driver</property>
<property name="dialect">org.hibernate.dialect.SQLServerDialect</property>
<property name="connection.provider_class">com.xpn.xwiki.store.DBCPConnectionProvider</property>
<property name="connection.pool_size">2</property>
<property name="statement_cache.size">2</property>
<mapping resource="xwiki.mssql.hbm.xml"/>

I hope someone has the answer to this missery.

Kind regards,
Jolanda Naafs