In my Office some person like using Pidgin as Chatting tools to connect to Yahoo messager.
Because my office using Squid as Proxy server, some modification of squid.conf is adding.

This line below (red bold) you must add on squid.conf.
acl SSL_ports port 443
acl SSL_ports port 5050acl Safe_ports port 80
acl Safe_ports port 21
acl Safe_ports port 443
acl Safe_ports port 70
acl Safe_ports port 210
acl Safe_ports port 1025-65535
acl Safe_ports port 280
acl Safe_ports port 488
acl Safe_ports port 591
acl Safe_ports port 777
acl CONNECT method CONNECT
acl shoutcast rep_header X-HTTP09-First-Line ^ICY\s[0-9]
acl apache rep_header Server ^Apache
Restart Squid : #service squid restart
Try connect from pidgin.
If any problem don't be ashame to put comment in this post. Thank's .