Can't RTMP connect to FMS from remote domain

I cannot connect to an FMS server from a client on a another domain using RTMP

Locally running a flash client that uses nc.connect(rtmp://...) to connect - works.

But when the client is in another domain I get NetConnection.Connect.Failed in the netconnection onstatus.

I've put crossdomain.xml files on my FMS folders that allow access from any domain (*).

Also the allowedHTMLdomains.txt and allowedSWFdomains.txt are set to allow any - though it's not just the live application I can't connect to, it's also any other app.

There are no firewalls blocking on the server. Port 1935 is available. FMS is set to listen to 1935.

The server is accessible with other protocols (http) - but with RTMP it only connects when I try to connect locally, as mentioned.

What other reasons or settings can cause the connection to FAIL?

The server is FMS 4.5 Developer Edition.