Ejabber, Jwchat and error 502

Hi.
I installed ejabberd and Jwchat on my Ubuntu Edgy, using this tutorial and this one.
Now I can connect to external Jabber server (i.e. Jwchat.org) but I can't using my local ejabberd server.
Using Firefox and Firebug, I realize that when I'm trying to login, Javascript send the request to http-poll but the answer is a 502 Proxy Error.

Can someone help me?
Thanks.