[Zope] Dreamweaver WebDAV & locking ??

I'm sure someone cleverer than I knows how this should work. Zope 2.4.0, Python 2.1.1, Dreamweaver 4.01 When creating a file for the first time with webdav DW attempts to lock the resource, Zope creates Nullresource-Lock item as a placeholder (all well and good, I thought) but then DW fails to upload the real contents claiming either 'Resource locked' or 'Resource not found'. I haven't been able to figure the system which selects one or other of these two replies. This smells of pilot error to me so please, anyone who sucessfully uses DW webdav, do you have a takeoff checklist ?? Thanks, Nigel.