VerifyError: Error #1014: Class flash.text.engine::ContentElement could not be found. in flex

That explains it then. This example requires the ContentElement, which is only present in FlashPlayer 10 and later. The example should require that -- when the project is set up, it can specify the minimum Player version it requires. Then if you try to run it on an earlier Player you get a warning that the SWF can't load on this Player, and it tells the user what version number is required. Try installing FP10, and it should work.