Error Type: TypeError Error Value: unsliceable object
Have you tried to use the newest Zope version? In 2.3.0 or so there was a bug that gave us the "unsliceable object" error for ZClasses that are based on "Image" or "File" (which should be similar to the DTMLDocument case). Newer versions work fine again.
NOTE: On one attempt, I modified the constructor input form to use 'addDTMLDocument' and the class method to use 'manage_edit' and 'manage_upload'. These changes got past the 'unsliceable object' error, however, when instantiating this class, I was unable to access the property sheets and views that I had defined. I was left with the default views defined for the DTML Document class.
I guess with this you actually create plain DTMLDocuments, not the new ZClass you have defined. This is why you don't get any of your customized propertysheets. BTW: What do you need a "DTMLDocument" ZClass for? I would not really know what it could be good for ... Joachim