This is not the same issue but it is very related.
The yahoo messenger, when you include it to the built-in messenger tp app, is acting nuts.
First, when your logged in, when you send chats to your contacts, the messenger app thinks its invisible. However, that person (where you sent the chat message) receives it.
Second, when you chat with someone and they reply, you don't receive any reply. When you try to login to your PC with your YM account, all those people who sent you the message keeps on coming in (as if it was sent as an offline chat).
Lastly, deleting the account and readding it fixes it, but you will soon have problems within a few minutes.