[Greasemonkey] Script firing twice?

[Dave Land]

Folks,

To learn about GM_setValue/getValue, I cooked up an idea for a script  
that would count how "lucky" I really  am when using Google by  
counting how often I click the 1st, 2nd, 3rd (and so forth) links...

So I started, as I always do, by writing a brain-dead simple script  
that just writes something using setValue, reads it back using  
getValue and logs what it read...

Oddly, I get two logged events, about 120 milliseconds apart from the  
following script:

// ==UserScript==
// @namespace   http://www.ryanland.com/greasemonkey
// @name    How Lucky?
// @include *.google.tld/*
// @description How lucky ARE you feeling?
// ==/UserScript==

now = new(Date);
milli = now.getMilliseconds();
GM_setValue("howlucky",milli);
GM_log("howlucky = " + GM_getValue("howlucky"));

/* -- end -- */

Why does it fire twice?

I turned off all scripts that target Google or "*" to see if one of  
them was doing a reload or something, but that doesn't seem to be it.

It's probably something stupid that one of my fine GreaseMonkey  
friends will point out in an instant.

Dave