I’ve always had problems configuring ICQ account in my pidgin in Debian. Somehow it never worked although I tried all these different combinations like “Use clientlogin” or “Use SSL”, etc, etc, etc. It never worked out of the box like it happens with Kopete in Debian KDE.
At some point I thought it was a problem of server as the default login server you have when adding ICQ account is login.messaging.aol.com. According to http://developer.pidgin.im/ticket/5450 the server is correct and it should work flawlessly.
Despite the message in the ticket I decided to try login.icq.com instead of login.messaging.aol.com because it is shorter, and it makes perfect sense for me (I have no idea what is aol, and as I am going to use ICQ protocol, it is logical for me to use login.icq.com as an address) and guess what? It works!