At any given time, I have at LEAST 10 tabs open in Firefox. It runs me around 200MB in memory. Something you're using, an add-on perhaps, is sucking memory like crazy. And I have a shit ton of add ons too.
The Only ADD-ons that i have is:
JAVA CONSOLE 6.0.17 + 6.0.16
MCAFEE SITEADVISOR 3.0
SKYPE EXTENSION FOR FIREFOX 126.96.36.19971
I noticed some how my web search got in my add-ons???
Also has anyone noticed: In firefox i'll be watching a video on youtube etc that the video will stop for a few secs but audio will still go and the little placement thing will still be moving, but the video will just completely stop and then it will go really fast, the video will try and catch up with the audio, it does it several times, no matter the length of the video. right now its doing it as i'm typing for some reason. I'll be typing and it will stop then go fast and its only every now and then. - weird huh?