For me (Late 2009 Macbook Pro, aftermarket 160Gb SSD, OS X 10.6.7, FF 4.0.1) it seems that there is something freezing the browser after sleep but after a long period of time (at least 5-10 minutes) it finally wakes up and works as usual. So there is no absolute need to force quit but I can understand why one would do it.

At first I thought that the reason would be with FF syncing as I got errors regarding that when the browser finally woke up but even after disabling sync the problem still persists.

Similar problem with my early 2011 MacBook Pro, OS X 10.6.7, FF 4.0.1. Firefox refuses to respond to some actions, like changing tab, creating new tab etc. Tabs can however be navigated with keyboard commands. After a minute or so the FF starts to function normally. Not sure if this is the same kind of problem as in above cases.

Im suddenly having the same problem as of 2 days ago after an update... any word on why this is happening?? 2011 MBP... Im going to stop updating

this has been happening to me for at least a week, and seems to be getting worse. firefox freezes upon startup, and then freezes maybe every twenty minutes or so when I'm actively using it, staying frozen for at least a minute or two. it drives me crazy. I have the most recent version of Firefox, and the 2010 MacBook Air.

okay -- it APPEARS upgrading to [[Firefox 7 beta|http://www.mozilla.org/en-US/firefox/all-beta.html]] works. I've downloaded it and no freezes for an hour.

ETA: aaand it's back to freezing again.