[Zope] adding zclass instances via dtml

[Cornelis J. de Brabander]

Probably I'm overlooking something very obvious, but I can't find out what.
I fail to add a zclass instance through dtml. I can add it in any folder I
want using the management interface though, but the dtml fragment below
raises an AttributeError with error value 'OLEenheid', which is the metatype
of my zclass. Traceback see below. Can anybody put me back on track?

 <dtml-call "REQUEST.set('id', 'ovo002')">
 <dtml-with "manage_addProduct['OLEenheid']">
  <dtml-call "OLE_add(_.None, _, NoRedir=1)">
 </dtml-with>

Traceback (innermost last):
  File E:\zope\243\lib\python\ZPublisher\Publish.py, line 223, in
publish_module
  File E:\zope\243\lib\python\ZPublisher\Publish.py, line 187, in publish
  File E:\zope\243\lib\python\Zope\__init__.py, line 226, in
zpublisher_exception_hook
    (Object: broddel)
  File E:\zope\243\lib\python\ZPublisher\Publish.py, line 171, in publish
  File E:\zope\243\lib\python\ZPublisher\mapply.py, line 160, in mapply
    (Object: Eenheid)
  File E:\zope\243\lib\python\ZPublisher\Publish.py, line 112, in
call_object
    (Object: Eenheid)
  File E:\zope\243\lib\python\OFS\DTMLMethod.py, line 199, in __call__
    (Object: Eenheid)
  File E:\zope\243\lib\python\DocumentTemplate\DT_String.py, line 546, in
__call__
    (Object: Eenheid)
  File E:\zope\243\lib\python\DocumentTemplate\DT_With.py, line 133, in
render
    (Object: manage_addProduct['OLEenheid'])
  File E:\zope\243\lib\python\DocumentTemplate\DT_Util.py, line 231, in eval
    (Object: manage_addProduct['OLEenheid'])
    (Info: manage_addProduct)
  File &lt;string&gt;, line 2, in f
    (Object: guarded_getitem)
  File E:\zope\243\lib\python\AccessControl\DTML.py, line 104, in
guarded_getitem
    (Object: Eenheid)
  File E:\zope\243\lib\python\AccessControl\ZopeGuards.py, line 151, in
guarded_getitem
  File E:\zope\243\lib\python\App\FactoryDispatcher.py, line 99, in
__getitem__
  File E:\zope\243\lib\python\App\FactoryDispatcher.py, line 102, in
__bobo_traverse__
  File E:\zope\243\lib\python\App\Product.py, line 137, in _product
    (Object: Products)
AttributeError: (see above)

Cornelis J. de Brabander
==========================================
Department of Education, Leiden University
P.O.Box 9555, NL-2300 RB Leiden
+31 71 527 3422/3401
brabander@fsw.leidenuniv.nl
==========================================