On Firefox, I click Tools, Addons, Extensions, Greasemonkey, Options, select my user script, click Edit, change the source code, click save, reload one of the included pages, but the script is the unchanged version.
On User Scripts, logged in, I click my username, Script Management, my script's name, Admin, Edit Code Online, change the source code, click save, the link to the install page, install and the script is the changed version.
How did you turn on Live Editing? While following Greasemonkey tutorials, this feature is not working... Are you going to use the "works on my computer" excuse? Should this be on the Stack Overflow sister site Super User?