NIGHTMARE
ANGEL OF DEATH
I used to use this addon: *addons.mozilla.org/en-US/firefox/addon/fastestfox-browse-faster/
It doubled the RAM consumption. Suddenly FF was consuming over 500MB RAM when it used to consume around 200-230MB. Removed it and problem solved.
@ NIGHTMARE: You should see which addon is causing the problem. Could you list your addons? I'll install those on my FF and check.
Here is the list of my addons--> Adblock plus, After the deadline, Flash video down loader, flash block, flashgot, Greasemonkey, Imgur Upload, Im translator, LastPass, SkipScreen, stylish, Wired Marker. There are four other but they are disable and one more thing while surfing FB my FF get stuck and freeze.