Crashing whenever using mx.controls.Alert.show

Question

Flex Project: Desktop (AIR)
Flex SDK: 4.1
Flash Builder 4
Problem: Whenever I use Alert.show even with the simplest strings passed it crashes showing the following error:
TypeError: Error #1009: Cannot access a property or method of a null object reference.
    at mx.controls::Alert$/show()[E:\dev\4.x\frameworks\projects\framework\src\mx\controls\Alert.as:566]
And it is pointing at Alert.as line:
var sm:ISystemManager = ISystemManager(FlexGlobals.topLevelApplication.systemManager);
How do I use this? What's wrong? Any fix?

Answer 1

It sounds like you're referencing a NULL object somewhere.  Any chance you could provide us with some sample code?  I just successfully tried the following out:
<?xml version="1.0" encoding="utf-8"?>
<s:WindowedApplication xmlns:fx="http://ns.adobe.com/mxml/2009"
                            xmlns:s="library://ns.adobe.com/flex/spark"
                            xmlns:mx="library://ns.adobe.com/flex/mx"
                            applicationComplete="init()">
     <fx:Declarations>
          <!-- Place non-visual elements (e.g., services, value objects) here -->
     </fx:Declarations>
     <fx:Script>
          <![CDATA[
               import mx.controls.Alert;
               public function init():void
                    Alert.show("This is a test", "My Alert");
          ]]>
     </fx:Script>
</s:WindowedApplication>
Thanks,
Chris