I have the same situation as "peronium"has with a few minor differences.( First, Firefox lags at start-up. A lot. I'd move on to doing other things, and then about five minutes later a Firefox window suddenly shows - but not a responsive one: one click and I'm thrown into the realm of "not responding". If I'm persistent enough, eventually I'll get a warning saying: "A script on this page may be busy, or it may have stopped responding. You can stop the script now, or you can continue to see if the script will complete. Script: chrome://browser/content/tabbrowser.xml:0" Stopping the script does not appear to resolve the issue. I've had this problem in the past, so I wiped and uninstalled Firefox from my computer, restarted, re-installed and restarted again. It seemed to work... for about one week, when the problem decided to arise again. There are only two settings I have altered: 1) do not remember history; 2) installed AdBlock Plus.) this seems to occur a lot in yahoo email but has happened on most sites as well.not very consistent though...