[otrs] Upgrading from OTRS 3.0 Beta1->Beta 2

I have started the upgrade process for my Beta 1 system (built originally on that version). When I access the app I now get this prompt on each page: Namespace Core.Form.Validation could not be initialized, because Core.UI.Dialog could not be found. I don't see any hints in the log files. Has anyone else experienced this? Hugh