[Zope] problem with property sheet interface and multiple selection

[Thomas Adams]

Hi all,

when I try to add an editable property sheet interface
for a propertysheet with a multiple selection property,
this runs into the error shown below:

Traceback (innermost last):
  Module ZPublisher.Publish, line 101, in publish
  Module ZPublisher.mapply, line 88, in mapply
  Module ZPublisher.Publish, line 39, in call_object
  Module ZClasses.Property, line 84, in manage_createView
  Module ZClasses.Property, line 188, in manage_createEditor
  Module ZClasses.Method, line 103, in manage_addDTMLMethod
  Module OFS.DTMLMethod, line 403, in addDTMLMethod
AttributeError: 'unicode' object has no attribute 'read'

Does anybody have suggestions?

Regards
Thomas

P.S.:
I'm currently working on (Zope 2.7.3-0, python 2.3.4, win32) under
Windows XP with Python 2.3.4 (#53, May 25 2004, 21:17:02) [MSC v.1200 32 bit 
(Intel)]