Facebook not working on iPhone 4s ios5.1.1

Hi all Sorry to bother you but i have a real iPhone crisis here.

I cant log onto facebook from my iphone 4s working on (ios 5.1.1) --- bot safari and facebook app are not letting me sign in, with any username or password ( i asked my friends to sign in even that did not work on my phone)

I also tried to sign in using chrome on iphone, same broblem. what happens is that in the browsers, it does not redirect as it should after i click log in and insteat shows me a blank page with a long web adresss nd des nothing. al other websites like gmail etc are working fine

in the facebook app , it gives me an error [ ERROR CODE 1: FBAPIERROR DOMAIN }

I dont know what that means, i have even tried to delete cache and history from setting,

there seems to be an incongruity between my phone and facebook domain or server, or something like that, coz rest of the (https) sites are working normally.

even in other apps such as instagram, the facebook extension is not working.

the problem is not speciifc to my fb account, i tried other accounts as well and i am able to access my facebook on my macbook pro.

PLEASE HELP ME !!!😟

PS I cant update right now , coz i have limited internet usage at high speed. i want to save bandwidth. so no ios 6 update suggestions please