I made some changes on the Connection Preference.
By overriding default server information, I used two different server as follows:
messenger.hotmail.com
gateway.messenger.hotmail.com
both with port 1863 or port 80(with "Use HTTP Method" checked)
I found that there is no way to connect using port 1863.
Port 80 works fine if I set my status invisible.
If the status is set other than invisible, connection won't keep alive longer than one minute...
Still sticky...