[plt-scheme] Problem with teachpaks

I have problems using gui.ss and draw.ss at the same time.
As a project my students have made a snake game using
only draw.ss. For extras I suggested they made a gui with
a highscore and a new game button. Alas, there are something
wrong.

The following illustrates the problem. I am not able to click
the button if the loop is on. Its on winxp version 203
(but you probably guessed that since I use get-key-event).

Is there a work around?

; advanced student language, draw.ss and gui.ss

(define (call-back event)
  (begin
    (display "foo")
    true))

(define (loop)
  (begin
    (get-key-event)
    (sleep-for-a-while 1)
    (loop)))

(start 100 100)
(create-window (list (list (make-button "foo" call-back))))
(loop)

Yours,
--
Jens Axel Søgaard