Seeing the same thing and after about 30 mins, %CPU will hit more than 300% then drop back down to 100% or 99%. At that point, FF4 is frozen. Could still click on the tab to close but the tab stays there. If I quit, the browser will close but the program is still active. Had to do a Force Quit to totally kill the program. Tried a couple of times and still the same. Did not see this problem when running the Beta. Did remove the beta and reinstall FF4, still the same.

Yup, didn't mention it in my original post but same problem with the program staying active and having to force close to kill it. I had the same issues with the beta though. Glad to see I'm not the only one with the issue and hopefully it will be fixed soon!

I have the exact same issue. What' interesting is that when using FF 4 in parallel to Google Chrome, if I access exactly the same pages, after only 10 min FF 4 consumes about 200MB whereas Google Chrome consumes only 60MB. There is really something to do with Firefox, please fix this.

I've tried restarting in safe mode and disabling all the plugins but the problem remains the same.

Last week FF 4 even consumed up to 1GB after only 4 hours. This just makes FF 4 un-usable compared to Google Chrome.