Thank you NautiWood,
it works!
After many months I've resurrected my player thanks to you!!!
I've uploaded the firmware to my ftp to be there forever for all the people who needs it. Look at here:
http://www.exclat.com/files/MP4_Digital_Player_9.1.51_firmware_s1clone.zip
Or from MyMPxPlayer.org:
Firmware: MP4 Digital_Player 9.1.5.1 (Glacier Like)