firefox streaming problems/ie,msn problem

i have problems with my firefox.it's the newer version.it shuts down immediately when i try to open a video through the browser,or even live radio.(though i can watch videos at youtube for example).same thing with opera browser.in addition my internet explorer shuts down immediately when i open it,and msn messenger shuts down when i log in, in 1 second.(though trillian works fine)
i have windows xp,updated constantly, avast antivirus and zonealarm pro firewall.through zonealarm i let every traffic of these programs,mainly firefox.
please help me.don't know what to do 3 months now.