A restart of Firefox fixed this.
My trusty and rusty old Microsoft mouse (a big old wired one, curvy) started acting funny toda, but in Firefox, not Safari.
If the scroll wheel is used the page just disappears. We love this mousey and i dont think it's available anymore. Also I am not sure a new one would fix the problem. Also, without touching the mouse, when i tried to fill in forms on this page, the page jumped but did not disappear. Im on a iMac, 10.5.8.
I had to edit in the thing about Firefox. It's hard to explain but the content of the page just disappears.