COMMUNICATION INTERRUPTED WITH WEB IDE or SERIAL TERMINAL

I am going to check.
Only 4 bits are used and connected on what appear to be right pins. (C5,C4, C0,C1,C2,C3).
I made a checklist of already used wires.
The remaining 4 wires are not used at all .
I'll begin to work out all the warnings and then let you know.

Maybe try executing the code after a timeout on onInit?
No the code was executed before a SetInterval()
Yes I put the flashing of the led inside the onInit() and this seems to cause problems to the serial communication on Mac OsX as soon as the USB cable is plugged in but not on Windows 7 ( strange… but I must check what is happening since this morning on the Mac )

If the USB cable is linked led doesn't flash
If the USB is uncabled , the LED flashes.
At the end of the trial the downloaded code was this :

var ON=1, OFF=0;

function LCD_bckgnd(status,pin) { digitalWrite(pin,status); }
function onInit() {
   var l=false;
   LCD_bckgnd(ON,E7);
   lcd.clear();
  lcd.setCursor(0,0);
   lcd.print(" Board OK …");
   lcd.setCursor(0,1);
  lcd.print("Led1 blinking.");
  setInterval( function() { l=!l; LED1.write(l);},500);
}

var lcd.c = require("HD44780").connect(C5,C4,C0,C1,C2,C3);

onInit();

What does it happens with using a timeout on onInit() ?
Which kind of things should be logically done inside on onInit() ?