[UPDATE] As of now the latest update on jaunty for the kopete package, the problem is fixed in the version 4:4.2.2-0ubuntu2.
It seems Yahoo! is changing their protocols for client connection. Heard somewhere this is done to disallow 3rd party clients like pidgin and trillian access yahoo’s messenger service. On my Ubuntu Jaunty, this has not affected pidgin yet! (looks like it auto adjusted) , but for Kopete I had to override the server connection to cn.scs.msg.yahoo.com and now its working fine.
Got the workaround from here.
Kopete is the only yahoo client on linux, AFAIK that allows video chat. Not sure if anything else has surfaced up yet. Haven’t been able to use Gyache yet with my webcam.