[Zope] Problems upgrading - broken ZClass instances

I'm moving machines and upgrading Zope, so I moved the old Data.fs* from machine A (zope 2.0.1) and moved them into an installation of 2.1.0b1 on machine B. As a result, all my ZClass instances are now broken - the say: recipes (This object from the unknown product is broken!) and I'm getting errors on startup such as ImportError: No module named *5imovKZn6trBy2xCM8ycbg== ------ 1999-11-07T08:26:06 ERROR(200) ZODB Couldn't load state for '\000\000\000\000\000\000\000\002' and in fact none of my ZClasses have that value. Any ideas?