Windows Live Messenger

Don't know if this is the correct place to put this question. I have windows live messenger operating on a computer using vista. I have to accounts or ids. On the first account all of my yahoo messenger contacts always appear offline and I cannot send them a message although they can send one to me. On the second account everything is fine. I see them, they see me and we message back and forth. It use to be this way on the first account, but something changed. I don't know what. For certain reasons I need to get the first account back operating properly. Can anyone help?