Problem with Firefox 3.5.3....one more

So,everything was still quite good recently,then I started to notice weird actin of Fireffox.
In the beginnings,I noticed that Firefox gets stuck when I open ccca 30 tabs,and then if I would decide to close a single one,problem would appear.I wasn't able to shut that one tab,and Firefox would be frozen on a 10-15 seconds.OK,so I found a solution not to open so many tabs,and I rather open 10 in Firefox,10 in Opera,and 10 in IE.(Opera and IE doesn't have that problem at my PC,but I'm stuck with Firefox because of all those add-ons).
Some time passed by,and now I can't even have 3 or 4 tabs open,because every few seconds Firefox freezes on a approximately 1/10 of a second,screen goes white like it will show a message that it won't respond any more,but it all passes by also in a blink of eye like it showed up,screen turns into normal colors,and let's go further surfing.
And it was all still quite tolerably till few days ago.I have to say that from time when Firefox started to act sluggish,I was pretty occupied and I was turning on my PC maybe 3-4 hours per weekends,what means that waiting on a peak of the problem wouldn't last 5-6 weeks then everything would be in state like today maybe already after a week.
Today,I can't even surf normally even with just one tab open,every 10-15 seconds Firefox freezes on a blink of eye or so,and it refreshes it self back in a second again.
I have tried to disable some of my add-ons but it is nothing better,and again,when I think better,I had all those add-ons installed even before,and there was no problem.
If it is important,I'm running Firefox 3.5.3,and I haven't made any significant changes since I have install it beside updating add-ons on a regular daily basis.
So my question is if maybe there is someone who had a problem like me,and how he solved that problem,or maybe anybody has a good advice?
Thanks for reading,and I hope that you have understood what I wanted to say,because my English isn't the best.
Cheers

sounds like one of those addons went rouge on you. I would disable them all and enable one then test the system. The close enable the next and test. Continue until you find the one that went bad. I've had addons go odd from time to time so if you can remember the last ones that updated then go for those first.

DarkXeno said:

sounds like one of those addons went rouge on you. I would disable them all and enable one then test the system. The close enable the next and test. Continue until you find the one that went bad. I've had addons go odd from time to time so if you can remember the last ones that updated then go for those first.

Huh,stupid me.I didn't even thought to do that but now when you say it...
Erm,and I forgot to say in my first post,at the same moment when I open Firefox,RAM usage of Firefox.exe process takes minimum 150Mb,and when I eventually open another one,two or more tabs,now it is nothing strange when I see firefox.exe use 500-600Mb RAM even when thee are just two or three tabs open,and CPU usage jumps up and down with no reason.