Did you try this firmware?
http://www.mympxplayer.com/dload.php...ile&file_id=46
That looks similar to yours. Try that.
The best way to recover your old firmware is to have had a BACKUP of it. Did you take a backup of you existing/original firmware before updating it?
Hopefully you are able to update the firmware using the link above. Or is your player 'dead' and can't be upgraded?