To replicate: - start firefox. Everything works fine - switch to another window, either using Alt+Tab or using mouse, switch back to firefox - vimperator no longer works. "t" or "o" do nothing, ":" does not switch to command line mode - to get vimperator back I can right-click and dismiss the dialog, go to menu and back to the website and few other things - next time I switch to another window and back to vimperator the problem reoccurs Ubuntu 14.04 firefox 32.0+build1-0ubuntu0.14.04. Vimperator 3.8.2