I too am having the same problem. And my eyesight should be fine. O_o
Basically it loads a fullscreen preview of the site, rather than in a box with the activate button on the top right corner, like I see in tutorial videos on some blogs.
It is really confusing.
I’ve tried it in Safari, Firefox, Camino, all giving the same result. I have not tried Internet Explorer on windows. Do I have to…?