Comment 2 for bug 998872

I don't have any extensions enabled. May be just one of those things that can fall under corner case hardware wise.
Tried on both 12.04 & a new 12.10 install, same thing. Seen with FF 10/11/12.

With a little care I noticed I can set up UF in a FF window with the same page having both the 'ubuntu' theme & cleanv3 available thru the back & forward buttons. Becomes quite obvious then.

I noticed someone mentioning the same in your beta thread, maybe I'll quote them & see if they're still seeing & what hardware, ect.

At the end of the day not really a big deal, particular if localized or a corner case. Opera works fine with SS with both themes. I guess that with the emergence of SS in gtk3 in many apps I've gotten used to having SS much more often than not.

Hardware here -
Dell 1330m, nvidia 8400m GS, powermizer set to max performance, tried with nvidia-current, nvidia-current-updates, nouveau