'Module not found' when trying to load any module

Hello,

I just received my new Espruino Starter Kit a couple of days ago.

When I tried to go through the tutorial on using the DS18B20 temperature sensor (http://www.espruino.com/DS18B20), I came across a weird problem: Apparently I can't load any modules. Here's what happens:

>require("DS18B20") 
ERROR: Unable to read file : NOT_READY
WARNING: Module not found

The same error also occurs when I try to load some other module from http://www.espruino.com/modules. The Modules/Config entry in the options is set to {"url":"http://www.espruino.com/modules","fileExtensions":[".min.js",".js"]} (which, I think, is the default value), and I am using Firmware version 1v48 and the Espruino Web IDE under MacOS.

Any suggestions on what I might try to fix this?

Alexander