I see a lot of ignorant posts like this; "My PC runs it just fine, your PC must svck". LOL.
Get a clue dude. A lot of people are running very similar specs to what you are and are having significant problems. I'm running an i7 920, a 5870, and 8GB of DDR3 and having some serious issues with FPS and connectivity.
Again it's
YOUR system.. as myself and others are NOT having the same issues as you..
I do this for a living for the last 25 years. longer than most of you have been alive I'd wager..
I know how to run and maintain my PCs and never have the issues that others seem to have on launch days.
over the years you'd be surprised of how many "bad ass PCs" I've been over to help a friend with that was having gaming issues only to find the so called uber systems were ill maintained and had crappy components or were "off the shelf " Dell or HP ready made systems. I've seen plenty of
garbage i7 based systems..
As the other threads have figured out its an ATI problem in this case. that's why well cared for well build Nvidia based rigs are not having any issues.
the few that are are most likely user or user PC issues period.