Arduino and VMUSIC2

I have trouble making the VMUSIC work with Arduino... Could some please give a hint?

Schematics:

void setup() {
    Serial.begin(9600);
}

void loop() {
    Serial.print("VPF test.mp3");
    Serial.print(13,BYTE);
    delay(10000);
}

Problem:
The VMUSIC turns on well but does not play any sound... All I want is to command the Vmusic from the Arduino.

I cable the boards as shown on the picture... I pulled-up the jumper pin to activate the serial UART mode instead of SPI.
The TX pin of the arduino seems to send the signal well, but the VMUSIC is not responding even if the LED is green.

Should I format my usb key to a specific standard?
I read that "Disks which do not have a sector size of 512 bytes are not supported".

Am I missing something obvious?

Thanks for your help.