interrupting LWW

When I'm debugging windowing code under LWW and I make a gross error, I get 
into an infinite error-redisplay-error-... situation.  The dialogs go by too 
fast to find out what the error is.  The only way I can seem to stop this 
run-away system is to use xkill (even the "Interrupt Lisp" doo-hickey doesn't 
respond).

It there a better way to cope with this situation?  (Other than not making 
errors :-).

The example below has a deliberate error that causes this run away behaviour.  
To run it, follow the instructions for getting opengl running, then compile 
this test and run (lesson1).

(I'm using mandrake 9.2 linux, if that makes any difference).

Thanks
pt

(load "host.lisp")
(load "OPENGL:compile")

(capi:define-interface opengl-interface ()
  ()
  (:panes
   (opengl capi:opengl-pane :configuration (list :rgba t)
	   :configuration '(:rgba t :depth nil :double-buffered t)
           :min-width 640
           :min-height 480
	   :display-callback 'draw-gl-scene  ; function to call for redraw
           :reader canvas ; use "canvas" as the name for fetching this pane 
from the interface
           ))
  (:layouts 
   (main capi:column-layout '(opengl) :default t))
  (:default-initargs
   :title "Lession 1"
   :auto-menus nil))

(defun lesson1 ()
  (capi:contain
   (make-instance 'opengl-interface)))

(defun draw-gl-scene (canvas); &rest ignore) deliberate error
)