can't add new room (with mod_muc)

I need some help with chat-rooms and mod_muc. I can refresh rooms list (at the moment I have none), but it's impossible to add new room or do anything else, doesn't matter if I'm trying it with ordinary user or jabber/muc admin. I searched Internet with google and I looked into a lot of related topics on this forum, tried a lot of configurations, but it didn't help me much. I'll be very grateful for any help in this matter.
I'm using ejabberd 2.0.1-6+lenny1 (on Debian Lenny) with pidgin clients (v. 2.5.5). Let's say my domain is example.com and name of my jabber server is im.example.com.

In fact, the jabber server im.example.com works behind the firewall. DNS server is directing traffic to the firewall and the firewall is forwarding ports 5222 and 5269 to the jabber server. Below I'm including the ejabberd configuration (I changed my domain name to example.com and admin user name to myadminuser):

override_acls.
{acl, admin, {user, "myadminuser", "example.com"}}.
{im, ["example.com"]}.
{loglevel, 4}.
{hosts, ["example.com"]}.
{route_subdomains, s2s}.
{listen,
 [
  {5222, ejabberd_c2s, [
			{access, c2s},
			{shaper, c2s_shaper},
			{max_stanza_size, 65536},
			starttls_required, {certfile, "/etc/ejabberd/ejabberd.pem"}
		       ]},
  {5269, ejabberd_s2s_in, [
			   {shaper, s2s_shaper},
			   {max_stanza_size, 131072}
			  ]},
  {5280, ejabberd_http, [
			 http_poll,
			 web_admin
				 ]}

			 ]}.
{s2s_use_starttls, true}.
{s2s_certfile, "/etc/ejabberd/ejabberd.pem"}.
{auth_method, internal}.
{shaper, normal, {maxrate, 1000}}.
{shaper, fast, {maxrate, 50000}}.
{acl, local, {user_regexp, ""}}.
{access, max_user_sessions, [{10, all}]}.
{access, local, [{allow, local}]}.
{access, c2s, [{deny, blocked},
	       {allow, all}]}.
{access, c2s_shaper, [{none, admin},
		      {normal, all}]}.
{access, s2s_shaper, [{fast, all}]}.
{access, announce, [{allow, admin}]}.
{access, configure, [{allow, admin}]}.
{access, muc_admin, [{allow, admin}]}.
{access, muc, [{allow, all}]}.
{access, register, [{deny, all}]}.
{access, pubsub_createnode, [{allow, all}]}.
{language, "en"}.
{modules,
 [
  {mod_adhoc,    []},
  {mod_announce, [{access, announce}]}, % requires mod_adhoc
  {mod_caps,     []},
  {mod_configure,[]}, % requires mod_adhoc
  {mod_ctlextra, []},
  {mod_disco,    []},
  {mod_irc,      []},
  {mod_last,     []},
  {mod_muc,      [
		  {host, "im.example.com"},
		  {access, muc},
		  {access_create, muc},
		  {access_persistent, muc},
		  {access_admin, muc_admin},
		  {max_users, 500}
		 ]},
  {mod_offline,  []},
  {mod_privacy,  []},
  {mod_private,  []},
  {mod_pubsub,   [
		  {access_createnode, pubsub_createnode},
		  {plugins, ["default", "pep"]}
		 ]},
  {mod_register, [
		  {welcome_message, {"Welcome!",
				     "Welcome to a Jabber service powered by Debian. "
				     "For information about Jabber visit "
				     "http://www.jabber.org"}},
		  {access, register}
		 ]},
  {mod_roster,   []},
  {mod_stats,    []},
  {mod_time,     []},
  {mod_vcard,    []},
  {mod_version,  []}
 ]}.

The /etc/hosts contains:

The /etc/hostname