"Hacking World of Warcraft" HelloAzeroth

I picked up a copy of "Hacking World of Warcraft" at Frys, and thought I'd try the tutorials.

Naturally I started at the simple "HelloAzeroth" tutorial. And, when I log in, NOTHING happens. It fails to do anything, not even give me an error.

It does show up in the list of addons when you click the addon button before entering the world.

It's a very simple two file add on.

In Folder HelloAzeroth

File 1: HelloAzeroth.toc
## Interface: 20200
## Title: Hello, Azeroth!
## Notes: The simplest addon ever.
HelloAzeroth.lua

File 2: HelloAzeroth.lua
message("Hello, Azeroth!");

Nothing happens when I log a character into the world.

I was expecting a message box.

When I mouse over it on the addon screen, it gives a tooltip with it's name and the Notes text.

I've experimented with an extra line to force a return after the last line in each file, but no effect.

I've disabled all other add ons.

LOL, I'd like to try some of the more meaty tutorials in the book, but I can't even get this to work. :)

Any clues?