Problem with buttons with image

In the examples directory there is a file "buttons.lisp" that shows 
buttons that display an image instead of text. Now, if I copy from this 
file, say
(defvar *do-button*
  (make-instance
   'gp:external-image
   :data
   #(66 77 66 ....

to my own file, I can equip my buttons with this picture. But of course, 
I want to use my own gif files, so I do:
(make-load-form (gp:read-external-image "img\\P.gif"))

and get a similar looking description:
(MAKE-INSTANCE (QUOTE GRAPHICS-PORTS:EXTERNAL-IMAGE) :DATA 
(GRAPHICS-PORTS::MAKE-DIB-ARRAY 68 :INITIAL-CONTENTS #(71 73 70 56 57 97 
16 0 16 0 145 0 0 239 239 239 148 150 148 255 0 0 0 0 0 44 0 0 0 0 16 0 
16 0 64 2 29 132 143 137 194 237 106 28 131 105 210 123 101 163 218 226 
15 114 194 215 141 74 233 45 93 38 133 46 86 0 0 59)) 
:TRANSPARENT-COLOR-INDEX NIL :TYPE :GIF :REAL-DATA T)

But if I plug this into the above code, I get an error:
Error: #S(GRAPHICS-PORTS::OTHER-IMAGE :POINTER #<Pointer: 
GRAPHICS-PORTS::GPIMAGE-POINTER = #x03512C78> :FILE 
#P"C:/Users/OLDENB~1/AppData/Local/Temp/PCLCBC6.tmp" :ALPHA NIL) is not 
of type GRAPHICS-PORTS::DIB-SECTION when accessing slot 
GRAPHICS-PORTS::HBITMAP.

Needless to say, that the gif files are allright, I use them in a java 
application on JButtons as well.

Yours,
Reinhard