from Pidgin:
- Manage Accounts (Ctrl + A)
- Select the Yahoo account from the list (assuming you’ve set one up before), and click Modify
- Click on Advanced tab, under the Yahoo Options, in the Pager server field replace scs.msg.yahoo.com with cn.scs.msg.yahoo.com
Try to connect to Yahoo messenger server again. It worked for me.
Link: http://kenno.wordpress.com/2009/06/20/pidgin-2-5-5-cannot-connect-to-yahoo-messenger/
