The LiveJournal login detection is greatly improved in the 1.1.8 version (BTW, the "What's New" page in the help file is out of date), but it still ask for the login name after it is given the journal URL. AFAIK, the subdomain is always the login name, except for the _ - conversion due to domain name rules.
ie, if the URL is http://rickybuchanan.livejournal.com/
then the login name is rickybuchanan - am I wrong? I often am :)