Whatsapp failing after update

after the last update, whatsapp doesn't really work. it can't complete the update when i open the app, says that the message history can't be recovered, and i cannot open, answer or write any new messages. the only thing i can see is the push notifications.
i have iphone with ios 3.1.3 and i can't really restore it since it's somehow jailbroken or soething (i didn't do it so i have no idea..)
please help, i just want my old version and my history back ;(