Yeah, Mozilla needs to get on the ball. FireFox has been causing me grief the past couple weeks too. They're gone for now. But it was destorying my computer. Ate up my processor while I was at work once. And took like half an hour to end task (I'm patient. Didn't feel like hard crashing).
Edit: I have the RAM problem too. Its like it calls dibs on the amount it uses total until you end a session. But I use tabs instead of windows so it's reasonable but apparently it doesn't matter. I've gotten used to closing everything out once in a while to clear things up a bit.