[Zope] IOError with ExtFile/ExtImage

Hi! I have a problem with the product ExtFile/ExtImage 1.1.X in Zope 2.3.3 I can´t add an instance of the product within another method. The following returns an IOError with the title: <dtml-call "manage_addProduct['ExtFile'].manage_addExtFile(title,description,file,content_type,0,REQUEST)"> The variables are all set correctly. Does anybody know what the problem is? Regards, Steffen Bergmann (Germany)