I tried "Substitute keywords" and it worked for me. That was before I used the Quick Locale add-on, after which point FF3 bailed out on me. I'm now using FF3 beta 5, because the only fix I saw so far was to uninstall FF completely (including private settings, I guess, as I already tried without them) before reinstalling.
Your keywords are saved in a file called prefs.js, on Windows that would typically be in C:\Documents and Settings\<your user name>\Application Data\Mozilla\Firefox\Profiles\<jumble>.default\, where "Application Data" is a hidden folder, so you need to set your folder settings (Explorer -> Tools -> Folder Options, 3rd tab) so as to see them. (For a different approach, see
here, or simply search your file system). Back up that file and you should be safe.
To know why scripts fail, open your browser's error console after starting the review, browse to the end, and look for a message in bold. If you could report that, I'd have something to go on.
To Transtic, one thing I'd do is to disable all GM scripts, except the Substitute one, then if that one works, turn the others on one by one, reloading the review page each time, to pinpoint which one(s) are culprit.