[Dovecot] multiple connections per imap/pop3 process in 2.0

[Mike Abbott]

When I set this in master.conf:
    service imap {
      service_count = 5
    }
I see this error when two imap users log in:
Nov 11 16:54:16 server dovecot[5432]: imap-login: Login: user=<user1>, method=PLAIN, rip=10.100.0.84, lip=10.80.0.163, pid=5573
Nov 11 16:54:31 server dovecot[5432]: imap-login: Login: user=<user2>, method=PLAIN, rip=::1, lip=::1, secured, pid=5573
Nov 11 16:54:31 server dovecot[5432]: imap(pid 5573 user user2): Fatal: setgid(2002) failed with euid=2001(user1), gid=2001, egid=2001: Operation not permitted
Then both users are logged out.

Is there another setting I have to change to enable multiple connections per imap/pop3 process in dovecot-2.0, or does it just not work yet?  I tried changing client_limit=5 but that had no effect.  (I suggest that master.conf needs more documentation.)  Thanks.