RemoteObject with a non AMF protocol

Hi !

I am trying to use RemoteObject with a non AMF protocol.
This is a section of my services.xml that is added to the compiler command line

<channel-definition id="core-services" class="ro.huddle.rpc.hessian.HessianChannel">
<endpoint uri="http://devserver:8080/spring-hessian/remoting/Services" />
</channel-definition>

here is how I use it:
service = new RemoteObject("coreServices");
service.concurrency = "multiple";
var t:AsyncToken = service.login("user","pass");
...
My problem is that only the first call works as it should, all the other calls don't even get to the server, the internalSend from the HessianChannel class doesn't get called except for the first time.

Anyone can help me with some documentation on how RemoteObject works ? The Flex2 help is very shallow on how the remoting mechanism works.

Thanks.