Almost every time I use FireFox 3.6.3 on my mac its okay for a while but them It becomes unresponsive and I get the mac busy icon. I usually have few windows and tabs open. I use these add-ons: LastPass Read it later Session Manager Flash Block BarTab Tab Mix Plus I have a 13" mid-2009 MacBook Pro with 2 GB of RAM. Sometimes it is so bad I have to force quit Firefox. Also another problem is with iTunes freezing.