Why do i can't sign into twitter on firefox?

[N]

i can log in via IE, but not firefox. I had this problem a few months ago as well and I searched on google and i found a simple remedy to change something in the setting and it worked, however now i can't remember what i did, and i can't find the article which helped me either.
does anyone know what should i do?

ps in the privacy the accept third party cookies is checked, also the option above it yet it does not log into twitter.
thanks
@born to be, no i don't get any error messages. when i write my email and password in the login form in twitter and hit enter, after a few seconds, what i see in firefox is like when you are not connected to internet and it tells you to check the connection and stuff.
born to be..., it is already enabled

[Born to be...]

Do you get any error messages? What exactly happens after you try to log in?

EDIT: Have you tried enabling JavaScript under "Content" tab?

EDIT: Have you tried clearing your cookies, history, formulas and temporary files for your browser?