Bindable bug?

I'm working on a Flex/AS3 game and I've noticed a weird bug. Some components will fail to appear when added to the app. Which components seems random-- for example a new HBox() might appear okay, but a custom component that is simply an extension of HBox might not show up.

After a lot of trial and error, I discovered the problem only shows up if I use the addition assignment operator or increment operator on a bindalble variable during the game's main EnterFrame loop.

For example:

PHP Code:

---

[Bindable]
public var entitiesUpdated:int = 0;

private function onEnterFrame(e:Event):void
{
        // This line causes the bug:
    ++this.entitiesUpdated; 
        // These don't:
    var updated = this.entitiesUpdated;
    ++updated;
    this.entitiesUpdated = updated;
} 


---

What's going on here?