URGENT – Unable to Login/Post Comment

I am unable to log into our blog (www.passionforcinema.com) and also cannot post or edit a comment/an article. I do not get any errors code. When I post a comment, I get a blank page. So do not know what is causing this sort of behavior. Our site has been down for last 12 hours, so any help which would resolve our problem would be great!

Thanks