If I push the "Create" button in "multiplayer" and write a room name the system reply to me "not connected"..so how can creat room? I would like to play with my freind on 1v1.

It may be a temporary problem .....
You can try to get a free play and write this in the chat (T)
/ jo (room nane) example / jo beginner
so you can create servers
if it does not work could be a temporary problem

edit
I forgot something
some names for rooms are prohibited
you could try some as
Pro, katana, aikido, or some names several

don't work...but thx

edit:

Tryed with simple and combinated names... U can creat room? If u dont can this is temporary problem but u can, i'm a noob ^^

That sometimes, happens it's annoying. Do this, type /jo "room name" when the message appears saying "not connected" press t then up on the arrow pad then enter to re-type the join message. Keep doing this quickly, eventually you'll get a room. That's what I do anyway. ;)