Instant messenger alerts

Since downloading the latest version of messenger the sound/pop up screen facility no longer works to tell me when someone has signed in. I have removed it/reset it back up both by the options facility and by right clicking on the contact but despite showing it as being set up I no longer get the sound or the pop up screen. The sound itself is working on the pc as when I press the option to play the sound everything is ok but it just doesn't work when someone signs in. Can anyone offer any suggestion as this is infuriating when working on another screen & I am waiting for someone to sign in?