[Genzo]

var params:Object=LoaderInfo(root.loaderInfo).parameters;

это не правильно , ты параметрам передаешь URLVariables!

public function VkRequest( action: String , viewer_id:int , params: Object = null)
		{
			this.viewer_id = viewer_id;
			this.variables = new URLVariables();
			this.variables.method = action;
			this.variables.api_id = this.api_id;
			this.variables.v = "2.0";
 
			this.variables.test_mode= "1";
 
			for (var i: String in params) {
				this.variables[i] = params[i];				
			}
 
			this.variables.sig = generateSig();
 
			request = new URLRequest( this.vk_url );
			request.method = URLRequestMethod.POST;
			request.data = this.variables;
 
			loader = new URLLoader();
		}
		public function send()
		{
			loader.addEventListener( Event.COMPLETE, onRequestComplete );
 
			loader.addEventListener( ErrorEvent.ERROR, onRequestComplete );
			loader.load( this.request );
		}
 
		private function generateSig():String
		{
			var signature = "";
			var params:Object = this.variables;
			var sorted_array: Array = new Array();
			for (var i: String in params) {
				sorted_array.push(i + "=" + params[i]);
 
			}
			sorted_array.sort();
			for (var key in sorted_array) {
        		signature += sorted_array[key];
      		}
 
      		signature = this.viewer_id + signature + this.secret_key;
      		return MD5.encrypt(signature);
		}
 
		public function onRequestComplete( e: Event )
		{
			trace(e.target.data);
		}