[plt-scheme] editor behaviour

Hi,

I have upgraded my PLT-Scheme to version 4.2.
In my program I have used to write into an editor% in the
following way:

  (let 
    ( (ed (send window get-editor)) )
    (send ed lock #f)
    (send ed move-position 'end #f 'simple)
    (send ed insert text)
    (send ed lock #t)
  )

(I wanted to write to the end of the editor.)
With the new version of PLT-Scheme it does not "exactly" work
as it used to do. It does some sort of buffering. It does not
write the text into the editor immediately.

Has anything changed? 
How should I do it "properly", if this is not the right way?

Thanks for any help.

Best regards,

Peter Ivanyi