[Zope] Poskey Errors and BTreeFolder

[Anton Stonor]

Hi there,

After five years with plenty of Zope/Plone sites running we are now 
facing our first ZODB problems: Poskey Errors popping up here and there. 
  And it seems that they are all related to BTreeFolder based objects, e.g.

* The CMF/Plone "Member" Folder
* portal_memberdata (the CMFMember version)
* Archetypes reference_catalog

We know how to find (fsrefs.py) and remove them, however new poskey 
errors are showing up from time to time.

Any ideas of how to hunt down what's causing this? And are BTreeFolders 
particular fragile?

/Anton Stonor