this badboy laptop i'm using has 1GB of RAM...clearly enough to run FIREFOX and AIM without crashing!....it is about 3 years old though...probably just part of the slow death they all take!Like the previous update, it uses a bit more resources than earlier versions. This drain is what leads to lockups and crashes.
So if you have any doubt about the RAM muscle in your system, I would suggest installing at least 256MB more added (about $20 in most places)
Otherwise, it's still easily superior to MSIExplorer thanks to the insulation from mainstream hacking attempts and spyware dumps.
It's an old fix but it helps with Firefoxes memory leak
http://www.howtogeek.com/howto/windows/fix-for-firefox-memory-leak-on-windows/