Cannot connect to xmpp:syndicon.de after upgrade to 2.4.2 from 2.1.1 (winXP)

[Rainer Glaschick]

After upgrading from 2.1.1 to 2.4.2 (WinXP installer),
connection to the XMPP server at syndicon.de fails:
system log for account xxx at syndicon.de/Home (jabber) connected at 19.06.2008 19:03:32
---- +++ xxx at syndicon.de/Home hat sich angemeldet @ 19.06.2008 19:03:32 ----
---- +++ xx at syndicon.de/Home hat sich abgemeldet @ 19.06.2008 19:03:34 ----

Is it possible to switch on more diagnose information?

Unfortunately, 2.4.2. automatically deinstalls the previous version,
so it would be tedious to try out several older versions.

-- 
Rainer