Can't Create server. why? :(

[HomerMix]

Yesterday I wanted to fly with a friend. So i tryed to create a server but it doesn't work.
On the screen where you can choose the server name and descrition, i keep getting "server could not connect to steam" when pressing ok and get back tu the menu.
I have no problem joining online servers appearing in the list. Direct connect to my friend using his external IP and port ended in a timeout.
I disabled the firewall and don't use a router.
I tried both internal and external IP in my NET settings.
Currently i'm running the latest beta patch. But i couldn't create any server before either.

Edit: When trying to create a server via the lobby i get the same error.

Any Ideas what could be wrong?