My yahoo messenger doesn't connect?!?

here's the problem: it's normal when you type your email add and pword. Then the "signing in as ___" is shown. I thought it will show my messenger list but it doesn't, instead it shows the pop-up for the invalid username or pword. I tried it several times but it's still like that. Tried firewall with no proxies, no network detection, all the four choices, even disabling my firewall for a while to see if it works but it still doesn't. Please help me 'cause I'm tired of the ads in Yahoo messenger for the web...