Thanks for replying to my post. This has been resolved now. By mistake I used

mybmp = new bitmap(stage.width,stage.height) instead of
mybmp = new bitmap(stage.stageWidth,stage.stageHeight)


One more strange thing I noticed, not related to this post, but I want to share that, when I used stage fullscreen code ,my simple buttons were not able to take mouseEvent.CLICK in html. Its working in html after I remove that code.

Cheers