HTTP proxy forbids port 5050 tunneling
If you are using the network under a proxy you will get these error while connecting to Yahoo messenger through Pidgin.
To fix this issue following change is required in pidgin proxy settings.
Go to Pidgin –> Accounts –> Manage Accounts –> Select your yahoo account –> Modify –> Proxy –> Here change the Proxy Type to No Proxy
This will fix the port tunneling issue.