Ankhor, I was never able to see these either until Gary's both ways stereogram. I clicked it to view it then right clicked to copy the image then pasted it in Xtreme. There I made it as big as I could.
I got up close to the screen and looked 1/3 up from the bottom of the pic and crossed my eyes. As I slowly relaxed them this wondrous 3D picture came into view - truly amazing. That is the first time it ever worked, and since then I can now see all of them (with some effort).
Give it a shot.
The both ways stereogram is here:
http://www.talkgraphics.com/showthread.php?t=45268