All of the standalone chumby-enabled devices with the exception of the dash use a media player called "bluetunes". The dash uses a stock Sony-designed media player, the same one they use(d) in their television sets and setup boxes. Apparently it was never anticipated by Sony that this player, when it was designed, would need to play user-defined URLs that require additional processing, since normally the stuff sent to the player is strictly controlled (typically by using the Sony supplied media apps that come with the TVs).
Even if I had the source code to that player to modify it, I can't update the version on the device because the firmware is locked and can't be updated without access to Sony's security keys.
Sorry about that.