Share 'Yahoo Messneger problem'

Since yesterday, my messneger gone crazy, I added this Yahoo id of a friend and now when I send her IMs she doesn't receive them or sometimes I don't receive hers, or in other chances none of us can receive messages sent by the other, it is really annoying, all other ids work well but it seems sometimes even that some of the others don't work either. Can anyone help me with this? I tried with ver…