[Zope] Upgrading to Zope 2.5 database problems

Hi all, Has anyone had problems when upgrading to Zope 2.5? I did exactly what I normally do when upgrading the product, but when I copy the database across and try to run Zope it stops itself after approximately 10 seconds. I can import the portals to the database created by the install and that runs OK but then all the dates are incorrect. I am currently running Zope 2.4.3. Spec: CMF 1.2 Python 2.1.1 Many Thanks James