No, non funziona con il player5.

Come si legge alla pagina http://www.macromedia.com/support/fl.../flashvars.htm

The FlashVars property of Macromedia Flash Player provides an efficient method of importing variables into the top level of a movie when first instantiated. This feature requires Flash Player 6 (or later). For information on passing variables with earlier versions, refer to Additional Information below.