If you try to open a bluetooth connection between your phone and a custom application (let's say something designed with bluecoves & java JSE...), you should have a look here if you can't get it work (connection refused)
http://code.google.com/p/android/issues/detail?id=5427

Solution was to specify the channel:

Method m = device.getClass().getMethod("createRfcommSocket", new Class[] { int.class });
BluetoothSocket connection = (BluetoothSocket)m.invoke(device, 1);