Hi,
first - this kind of code:
krpano.get("plugin[video]").onvideoplay=this.handleVideoPlay
could only work in HTML5!
In Flash it would fail (do nothing) because the returned objects from the get() call are not linked to the original Flash Actionscript3 code!
Second check the the usage of the 'onvideoplay' in the xml code, it might get overwritten and also WHEN you are setting the event.
Best regards,
Klaus