error in hibernate persistance service

Hi everybody,
though Aleks' instructions stopped right were I had already arrived, I'm 
trying to go ahead on my own. Now I'm stuck after building the project 
with "ant nonetinstall".
The tomcat server starts regularly, but, when I try the "createdb" 
model, I get the following error:

null, Could not return a reference to the Component 
(Key='org.keel.services.persist.PersistentFactory/*')

Any clues?
Ciao
Maurizio