Here's another image of linearly moving dots.
Somewhat humorously, when I first saw that image I saw that the dots moved in lines, but it took ~15 seconds to see the pattern.
Are you at all colour blind? I imagine that the colour really helps with the illusion, so being even partially colour blind might weaken the effect.
Maybe a tiny bit? My wikipediaing brought up the ishihara color blindness test, which I had no problems with. However, on the red-green test images, I could see the numbers that should be seen if I have red-green color blindness, they were just less contrasted than the normal vision ones.
Additionally, I seem to perceive the boundary between pink and red differently than most people.
Edit: Oh, and if you remember that hue ordering test that someone here posted a while back (you can find it with google) I only got 4 wrong on that.