URLLoader bug with AIR SDK

Environment:

Flash Builder 4.7

AIR SDK 3.4

Mobile ActionScript project

Problem severity:

Use URLLoader class to get data from server; use URLVariables to send data containing a single field (Note, this issue happens only when you're sending only one field), as:

var urlVariables : URLVariables = new URLVariables();

urlVariables.contactid = "mycontactid";

var request : URLRequest = new URLRequest();

request.data = urlVariables;

request.url = "https://myserver.com/flex/GetContactDocument?OpenAgent";

var loader : Loader = new URLLoader();

loader.addEventListener( Event.COMPLETE, onSuccess );

loader.addEventListener( IOErrorEvent.IO_ERROR, onIOError );

loader.load( request );

Everytime it turns into IOErrorEvent returning stream error with the used URL path. I eventually noticed it didn't add any "&" after the URL! So what was supposed to be is this:

https://myserver.com/flex/GetContactDocument?OpenAgent&contactid=mycontactid

But instead URLLoader seeing this as:

https://myserver.com/flex/GetContactDocument?OpenAgentcontactid=mycontactid

Note, there's no & sign after OpenAgent word!

This doesn't happens when there are more then 1 fields in URLVariables class! This is strange, and looks like a bug to me!

Any suggestion would be appreciated. Thanks!