Ok, probably I fell in a pitfall I was not aware of. I changed the ECHO behavior of the BlueGIGA chip and probably that was not supposed to happen.
In fact, a quick browse of the bootloader code reveals that it doesn't set the ECHO parameter, and from all the example I've found, that use "SET CONTROL ECHO 0", I suppose that the bootloader itself expects no echo of commands or events on the input line.
Unfortunately changing the ECHO value means that the bootloader behave differently and I'm not able to upload scripts anymore (Arduino gives "programmer is not responding").
What option do I have now? should I use an AVRISP mkII programmer? or is there a simple way to revert the BlueGIGA chip to its default configuration?
Inverno Learning it the hard way ^_