Back/Forward button (ALT+Left/Right) broken Rated 5 out of 5 stars

In principle this is a very useful addon. Unfortunately, it breaks the forward/backward buttons (and the keyboard shortcuts CTRL+Left/Right). Deactivating the addon seems to fix the problem.

EDIT: Sorry, I meant ALT+Left/Right. But it looks like it is an incompatibility with another addon. On one computer it works, on another, it does not :-(

(Perhaps you might want to use some bug tracker like the issues on github, because 783 post/53 pages on mozillazine are too much to search through if this bug was already reported)

Ez az értékelés a kiegészítő előző verziójához készült (1.2.1.1-signed). 

CTRL+Left/Right for triggering back and forward buttons does not work for me without this add-on either. Are you sure, you are not using another extension to achieve that?
Or is this some OS feature not available cross platform?

Edit:
Using ALT+Left/Right works fine here.