Flex mobile error - client.error.deliveryindoubt

[desup]

Hi, I'm developing app for Smartphones (iOS, Android and Blackberry)
I'm contacting my server for php script, with local server, everything works fine, but with remote, I'm still getting an error:

faultString="Channel disconnected"
faultCode="Client.Error.DeliveryInDoubt" faultDetail="Channel
disconnected before an acknowledgement was received

I have found out, this can happen if there is an error in php class.
But It looks fine:
This is the PHP

I'm trying to get hello() function,
calling it like that:

        helloResult.token = mailclass.hello();
         var a:String = helloResult.lastResult;
         msg.text = a;             

Do you know where is the problem?
If not, can you just give me a definition of this error?
Thanks :)