Yahoo IM Won't Display in Post Box

[nprfairway]

I saw this same question was posted before but expired unanswered......trying again. Yahoo IM messages won't show in post box. I can see what I type but when I hit send....it disappears. Can see my contact is typing but those messages don't post either. Have reinstalled twice, checked font color and all settings within IM r/t "viewing, showing etc." It has worked fine for a couple of years then one day...nothing. In the latest version that I just downloaded......I can see a portion of the message in the little screen that pops up at the bottom of the screen to let you know someone is sending a message.....but nothing in the main post box. Any ideas welcome.