Hi there ! I am working on my product ZExternalNews (http://www.zope.org/Members/odeckmyn/ZExternalNews). I have a problem that I did not have anticipated ! My product is made of 3 classes: 1/ ZExternalNewsManager (usually one per site), folderish that contains several ZExternalNewsChannel 2/ ZExternalNewsChannel (several per Manager), itemish. Contains 2 persistent properties (title and url) and a _v_items, a list of ZExternalNewsItem 3/ ZExternalNewsItem a very simple Python class (no inheritance from zope nor ZODB). It handles an atomic news item (like a single news item in slashdot for example). When ZExternalNewsManager starts, I also "fork" a thread that (simplified) does : while 1: MyManager.Refresh() sleep(MyManager.delay) Where MyManager.Refresh is a loop that calls refresh on every channel. This would work in a wonderful land...but not in real life. I've been searching for hours now... My problem is : It works for some time (sometime 10sec, sometimes 2 hours, sometime 10 min...), and then, I got a lot of : 2001-08-07T17:36:04 ERROR(200) ZODB Couldn't load state for '\000\000\000\000\000\000WG' Traceback (innermost last): File /isp/zope/newfun/lib/python/ZODB/Connection.py, line 508, in setstate AttributeError: 'None' object has no attribute 'load' (a lot of = one per ZExternalChannel instance) and a last : Exception in thread Thread-4: Traceback (innermost last): File "/usr/local/lib/python1.5/threading.py", line 376, in __bootstrap self.run() File "/isp/zope/newfun/lib/python/Products/ZExternalNews/ZExternalNews.py", line 454, in run self._manager.Refresh() File "/isp/zope/newfun/lib/python/ZODB/Connection.py", line 508, in setstate p, serial = self._storage.load(oid, self._version) AttributeError: 'None' object has no attribute 'load' After hours of thinking, I think this is because ZODB ask my objects to go to sleep (is this DEACTIVATING ?). The last modification I made was to implement __setstate__ so that _v_* attributes are declared there : I thought it would be ok after that. It is not :( Please help me ! It is quite a frustrating experience ! Do not hesitate to Is there a document I should read before understanding ? I think I've read quite a lot of things until now ! ;) Attached is the latest version of the .py. Other part of the product is downloadable here : http://www.zope.org/Members/odeckmyn/ZExternalNews Thanx for your support. Olivier. (this question was posted 2 days ago on zope-dev, without answer, so I try here ;-D )