When I try to login after upgrading to 0.4 beta, I am simply returned to the login page without any error message.
All I can see in the logs is a search for the session :
[09-Jun-2010 10:31:41 +0200]: query(1): SELECT vars, ip, UNIX_TIMESTAMP(changed)
AS changed FROM session WHERE sess_id = 'XXXXXX'
IMAP and SQL debug options are activated, but apparently, it doesn't go as far as an IMAP request, it gets stuck trying to setup/retrieve a session.