did i encounter a hibernate bug or do i have an error i dont see:

select enty.number from EntityAliasName enty
  where enty.myId in
  (
    select cons.myId from Consens cons where cons.number in
    (
      select ord.number from Orders ord where ord.customer = :customer 
      and ord.creationDate <
      (
        select max(ord.creationDate) from Orders ord where ord.customer = :customer
      )
    )
  )

what i do get is the following:

org.hibernate.util.StringHelper.root(StringHelper.java:257)

Caused by: java.lang.NullPointerException
        at org.hibernate.util.StringHelper.root(StringHelper.java:257)
        at org.hibernate.persister.entity.AbstractEntityPersister.getSubclassPropertyTableNumber(AbstractEntityPersister.java:1391)
        at org.hibernate.persister.entity.BasicEntityPropertyMapping.toColumns(BasicEntityPropertyMapping.java:54)
        at org.hibernate.persister.entity.AbstractEntityPersister.toColumns(AbstractEntityPersister.java:1367)
        at org.hibernate.hql.ast.tree.FromElement.getIdentityColumn(FromElement.java:320)
        at org.hibernate.hql.ast.tree.IdentNode.resolveAsAlias(IdentNode.java:154)
        at org.hibernate.hql.ast.tree.IdentNode.resolve(IdentNode.java:100)
        at org.hibernate.hql.ast.tree.FromReferenceNode.resolve(FromReferenceNode.java:117)
        at org.hibernate.hql.ast.tree.FromReferenceNode.resolve(FromReferenceNode.java:113)
        at org.hibernate.hql.ast.HqlSqlWalker.resolve(HqlSqlWalker.java:854)
        at org.hibernate.hql.antlr.HqlSqlBaseWalker.propertyRef(HqlSqlBaseWalker.java:1172)
        at org.hibernate.hql.antlr.HqlSqlBaseWalker.propertyRefLhs(HqlSqlBaseWalker.java:5167)
        at org.hibernate.hql.antlr.HqlSqlBaseWalker.propertyRef(HqlSqlBaseWalker.java:1133)
        at org.hibernate.hql.antlr.HqlSqlBaseWalker.selectExpr(HqlSqlBaseWalker.java:1993)
        at org.hibernate.hql.antlr.HqlSqlBaseWalker.selectExprList(HqlSqlBaseWalker.java:1932)
        at org.hibernate.hql.antlr.HqlSqlBaseWalker.selectClause(HqlSqlBaseWalker.java:1476)
        at org.hibernate.hql.antlr.HqlSqlBaseWalker.query(HqlSqlBaseWalker.java:580)
        at org.hibernate.hql.antlr.HqlSqlBaseWalker.selectStatement(HqlSqlBaseWalker.java:288)
        at org.hibernate.hql.antlr.HqlSqlBaseWalker.statement(HqlSqlBaseWalker.java:231)
        at org.hibernate.hql.ast.QueryTranslatorImpl.analyze(QueryTranslatorImpl.java:254)
        at org.hibernate.hql.ast.QueryTranslatorImpl.doCompile(QueryTranslatorImpl.java:185)
        at org.hibernate.hql.ast.QueryTranslatorImpl.compile(QueryTranslatorImpl.java:136)
        at org.hibernate.engine.query.HQLQueryPlan.<init>(HQLQueryPlan.java:101)
        at org.hibernate.engine.query.HQLQueryPlan.<init>(HQLQueryPlan.java:80)
        at org.hibernate.engine.query.QueryPlanCache.getHQLQueryPlan(QueryPlanCache.java:94)
        at org.hibernate.impl.SessionFactoryImpl.checkNamedQueries(SessionFactoryImpl.java:484)
        at org.hibernate.impl.SessionFactoryImpl.<init>(SessionFactoryImpl.java:394)
        at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1341)

using: Hibernate 3.3.2.GA / postgresql