[Zope] Wierdness with ZCatalogedObject product

[Nigel Head]

This one must be obvous, but it's sure got me !

ZCatalogedObject product, on pristine Zope2.5.1 win binary ditribution.

Where tstObject is an instance of ZcatalogedObject, calling (from a python script):

 container.tstObject.manage_changeProperties({'prop1':999})

gets me a 

 TypeError, manage_changeProperties() takes at most 2 arguments (3 given)

on the line where PropertyManager.manage_changeProperties() is called from within ZcatalogedObject.manage_changeProperties(). Signatuere is the same for both. 

At this point I solicit tips for what could be causing this message, which appers to be manifest rubbish to me (at least after breaking my brains on this one for so long). Can't see the wood for the trees, probably!

Thanks in advance,

N.