[Zope] problem turning off permission acqusition

[sathya]

I have a file object (pdf type) which should be viewed only by a certain role.
So I want to turn  of the permission acquisition for anonymous users as they
have view permissions in the top level folder. However when i I try to change it
I get an  Error

error type : attribute  
error value: tag
Can anybody shed some light on this ?

Thanks 
sathya
  -- 
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 necessity is the 
mother of invention
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