A colleague of mine has developed an external method and installed it as a SiteAccess access rule. He made a programming error that caused a TypeError exception to be raised. He recognized his fault and corrected the external method. Then, the strange behaviour started: The access rule sometimes worked correctly but sometimes raised the old TypeError exception. I had the impression as if some threads used the new and some other threads continued to use the old version of the external method. We flushed the cache, but to no avail. My colleague finally reported, that renaming the external method and reinstalling the access rule fixed the problem. For me, it looks like a persistence bug. Problem context: * Zope 2.1.6 (sorry for the old version) * running in production mode, the external method was "refreshed" after modification with the "edit" button. Did you ever see something similar? Dieter