I have the same problem, but I'm on Firefox Aurora 15.0a2 (2012-07-07)

I've got a similar/the same issue. Firefox will be highlighted when I launch it, but when I type in certain websites (CNN, Facebook, and Gmail are the worst offenders), those sites will load, and then it's as if I've clicked the desktop. This didn't happen until I upgraded (?) to Firefox 13 a few days ago.

It pretty much happens on the first website that I get on and is not website specific. I haven't tried disabling any add-ons. So I will do that next. If I don't follow-up with another post, it means that it did not do the trick. Otherwise I will post that it worked.

I am running 14.0.1 on Win7 x64 Professional and this issue is still happening. Very frustrating. I only have a couple of add-ins and I went down the path of disabling them, but doing so did not fix the issue. I first noticed it in the 13 versions.

I finally found the plug-in that is causing this issue for me. The plug-in I confirmed for my system is "Shockwave Flash 11.3.300.268", which is the latest available now. Disabling this one plug-in fixes the issue for me. Hopefully an update from Adobe will address this.

Awesome, disabling the Shockwave Flash plug-in worked for me as well. Thanks!