Same situation here, I bought 2 Itouch one is working fine and connecting to yahoo messenger, the other is giving me the same error, all the logins works fine on the PC.
2x Itouch 3G 8Gb
I already restored the second Itouch with factory defaults, checked router (internet works fine), and uninstall and reinstall app.
I've had the same problem with my son's iPod touch (8gb, 2nd-gen).
He can’t sign in to the Yahoo! Messenger app.
When he tries he gets this message:
*Yahoo! Messenger Sign-In Problem*
*Failed due to an known reason.*
*Please try again.*
(Yes, it says "an known reason".)
He is using the correct credentials. In fact, I tried with a wrong password and the app told me it was incorrect. I can sign on with my account with no trouble, and his account won’t work on my iPod, either. He can, however, log in just fine on our computers (Mac & PC) and the Yahoo! app (not messenger) on his iPod.
I tried both of his sisters’ accounts, as well, and neither of them work, either. I can only deduce the problem stems from the fact that +they are all Family Accounts+.
I’d love to hear an explanation as to the cause of this problem. Maybe the Messenger app is confusing itself with chat (which is restricted for Family Accounts)?
Of course, I’d love even more to see this particular bug squashed.
I have posted this message on the Yahoo Messenger blog, but received no response.
I am having the same problem and have come to the same conclusion that it's a family account. I have contacted Yahoo directly about this and I'm waiting for a response. When I get one I will "cut/paste" it here and hope it helps. 🙂 If anyone from Apple reads this, Thanks for a great product, my son and I love the iPod Touch.