Did you try the long-press at boot mentioned here: http://www.espruino.com/Puck.js#firmware-updates
I just uploaded the latest firmware from http://www.espruino.com/binaries/travis/07ae7710e3cd84e7773a7faba3124b3a6c9de85f/ and it works perfectly on my Puck.js
@Gordon started
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
Did you try the long-press at boot mentioned here: http://www.espruino.com/Puck.js#firmware-updates
I just uploaded the latest firmware from http://www.espruino.com/binaries/travis/07ae7710e3cd84e7773a7faba3124b3a6c9de85f/ and it works perfectly on my Puck.js