[Zope] Problems with Versions and Zope 2.5.X

Hello! I´m working with Zope 2.5.0 for a while now. But I have a problem to work with versions. Sometimes I get the following error when I try to work in a version and then "view" a object: Error Type: Unsupported Error Value: TemporaryStorage is incompatible with versions Does somebody know this problem. It´s not always coming up so I can´t reconstruct it. When I quit working in the version in such a case, refresh the Browser, and start again working in the version, the error is away. I don´t understand it and hope that somebody knows the solution. Bye Steffen