authentication in web interface does not work

Hello,

i am the proud owner of an shiny new ejabberd-1.1.3 server.
I can register users and the server works like expected, except the web interface.

The host ejabberd runs on, has the name kermit.adomain.lan
The ejabberd domain is jabber.adomain.lan
{hosts, ["jabber.adomain.lan"]}.

I have configured two admin users in ejabberd.cfg like so:
{acl, admin, {user, "admin", "jabber.adomain.lan"}}.
{acl, admin, {user, "walter", "jabber.adomain.lan"}}.
{access, configure, [{allow, "admin"}]}.

I registered admin and walter with ejabberdctrl.

ejabberd@kermit:~> ./ejabberdctl jabber@kermit status
Node jabber@kermit is started. Status: started
ejabberd is running

(ejabberd and ejabberdctl are started with -sname)
I have also a CNAME Record for jabber.adomain.lan which points to kermit.

I can reach the web interface via jabber.adomain.lan:5280/admin but i can NOT log in.
The login should work with admin@jabber.adomain.lan i think, but i does not.
Every time i get only "Not allowed".
I tried all combinations of usernames and host- and domainname i could think off.
The logfiles are of no help because only the http-request is logged, no errors.

I also reinstalled ejabber several times, i deleted the Mnesia-DB an the erlang-cookie
without getting access to the webinterface.

I can use the usernames admin and walter with jabber-clients and they have admin privileges,
but i can simply not get the admin web interface to work.

Now i am stuck - and shure need some help to get this working.

regards
ito