Tested with Firefox 3.5.8 against sameplace.cc (eJabberd?) and Psyced.
The latest mention of STARTTLS:
http://github.com/bard/sameplace/commit/d6f5f8bd71a8d52d21bc696d0e1951ede824a031
says it's no longer default because of a problem with Firefox. But it
worked for me with an existing PSYC account and a new XMPP account.
Also, the wizard interface doesn't switch port when STARTTLS is
selected, you have to do it manually.
Hope that helps,
==
hk