I am trying to help someone to restore some data.
I have the var folder, but I am not sure which Plone version they used. Is it possible that this error can come from 'wrong versions'. I tried with 5.1.6 and it give me this:
/buildout-cache/eggs/ZODB-5.3.0-py2.7.egg/ZODB/serialize.py", line 615, in getState
_pickle.UnpicklingError: NEWOBJ class argument isn't a type object
PS: Content types are Archetype, I think