As with the majority of DVD players, most CD-Rs won`t play on the 511, as the laser unit can`t physically read them. The only option is to buy a new player (one which is advertised as being capable of playing CD-Rs).
If you burn CDs yourself, you may have some luck using CD-RWs, and certain brands of CD-R such as Princo and Vivastar may be *just* within tolerance for the 511`s drive.
Mike