Menu button no longer works when this is installed

[jerry1970]

I installed this addon, then the menu button (the button at the far right on the toolbar where the address bar is) no longer works. I disabled this addon and the menu buttons works again.

Firefox 36.0.1, this addon 20110717.

[jmdejong]

Same problem here, I'm on Firefox 38.0.1 on Arch linux
On ubuntu 14.04 with Firefox 38.0 I do not have this problem (nor had I ever had this problem in earlier versions)

EDIT: by now the menu button works while the add-on is enabled, and earlier today it didn't work while it was disabled.