Yes, I do have the latest version of Greasemonkey (4.8), and the script works now after removing the apostrophes! It would be really great if this script becomes a standalone add-on.

Thank you for your quick and detailed replies and for solving the problem. We all appreciate that you're keeping this fantastic script updated all these years. I can't imagine using IMDb without it.

I only have 6 addons on Firefox none of them is related to IMDb and tried disabling all of them but it still didn't work. This is the only script I have installed on Greasemonkey.

While looking at the JS console I found this error related to this script, does it help identifying the problem?!

Could not execute [Greasemonkey script http://www.flickr.com/photos/ricardo_ferreira/2502798105//IMDb 'My Movies' enhancer; version 1.46] 
 missing ) after argument list execute.js:29:15
    executeUserscriptOnNavigation moz-extension://7fdfbbb9-997f-4163-a852-a6aa8a46e506/src/bg/execute.js:29

I'm not sure if the script still works with others, but it doesn't work with me. The top buttons (refresh, clear highlight.. etc) don't appear after refreshing Firefox and re-installing the script. (Firefox 67.0)

When I opened the javascript console (Ctrl+Shift+J) on the IMDb list page, I found nearly 40 errors and 120 warnings. I'm not sure what do they mean though.

It works perfectly with FF 57. We can't thank you enough for keeping this amazing script updated.. We really appreciate it.

IMDB has redesigned their list page, and the top buttons (refresh, clear highlight.. etc) have disappeared. Also the script doesn't work with Firefox anymore, even when the buttons used to appear. This script is the most useful thing I've seen for IMDB, and I really hope Ric would update it.