Socket connections blocked... (sandbox violation)

I'm having trouble with Flash Player 10, regarding opening of sockets. I have a socket server responding on port 843, my custom port and a web server hosting a crossdomain.xml file.

The problem is that when I try to run with the debugger, it won't even attempt to make a connection.

The policy log shows this:

OK: Root-level SWF loaded: file:///xxxxx/Main.swf
OK: Searching for <allow-access-from> in policy files to authorize data loading from resource at xmlsocket://xxxxx.com:53280 by requestor from file:///xxxxx/Main.swf
Error: Failed to load policy file from xmlsocket://xxxxx.com:53280
Error: Request for resource at xmlsocket://xxxxx.com:53280 by requestor from file:///xxxxx/Main.swf has failed because the server cannot be reached.

The error is this:

Security error: [SecurityErrorEvent type="securityError" bubbles=false cancelable=false eventPhase=2 text="Error #2048: Security sandbox violation: file:///opt/Develop/glig/Flash/Widgets/chat/Main.swf cannot load data from xxxxx.com:53280."]

The sandbox mode is: localWithNetwork

The flash player version is: 10,0,22,87

I also used the line Security.loadPolicyFile("xmlsocket://xxxxx.com:53280"), but without success.

The remote server is reachable and responding to <policy-file-request/>, but does not register any connection attempts.

This all worked perfectly fine with version 9, where it would do a http request for crossdomain.xml. According to all the documentation I've read, my approach should work, but the player isn't even attempting to connect.

Does anyone have an idea?