This bug is inside Nvidia's XRender acceleration. Set:
Option "RenderAccel" "0"
at nvidia driver options at xorg.conf to fix this.
If someone from Nvidia is reading this topic, try this too:
It freezes without crash. This application requires imlib2 to build successfuly.
Nvidia's render acceleration works in 99% appliactions I'm using. But if any app makes heavy use of many XRender functions freezeing happens.
web: firefox 18.104.22.168, seamonkey 1.0.4 (freezing when "RenderAccel" "1", no freezing"RenderAccel" "0")
web: konqueror 3.5.4 (no freezeing, "RenderAccel" does not impacts at all)
Nvidia driver 1.0-8774
If someone filled firefox or other bugreport please add link to this topic there. The less we waste developers' time the better apps will appear. Firefox or other browser does not look broken.