video subsistem crash visitin a web page with FF4

I cannot give any explanation, but I can reproduce it every time.

clicking on the image of the page below to get the image in full size
http://postimage.org/image/bmoa6ex0/
(it is the mirror of a newtonian telescope)
The video system start flickering and everithing lock and crash.

Hard reset needed.
Sometimes also altgr+K+shft+print work... but not always...