v5.1.0 broken with firefox 13.0.1 Rated 5 out of 5 stars

I have a set a button with a customized menu.
With firefox 13.0.1 and the latest version (5.1.0), only 4 items of the menu are shown, and none of them are clickable.

Moreover, there's a bug that makes the menu get duplicated (the same 4 entries are added) every time the menu button is clicked.

So, if I click the button 10 times I have a menu with 40 repeated entries, and none of them can be clicked.

Thanks for this great addon, I'm using it for months.
In combination with 'Menu Editor' it provides a very clean and minimalistic layout.

This review is for a previous version of the add-on ( 

There are some steps that can help me to figure the issue out.
1. Restart your Firefox.
2. Ctrl + Shift + J
3. Click Clear button and choose All in Error Console.
4. Click Firefox Button. If the issue occurs, close the menu and click the button again.
5. Copy the errors in Error Console and post them in the discussion forum.