Yesterday, when I started Firefox, I noticed that the Chrome’s interface shown up instead. I thought I picked the wrong icon, closed the window and tried to start Firefox again: no more Firefox icon in the start menu. I pressed the Windows key, typed Firefox, picked the Mozilla Firefox result and pressed Enter. I got Chrome again. Tired of stupid bugs making absolutely no sense, I closed the window and removed Chrome from my computer. I tried to start Firefox again: Chrome started once more. So even the removal failed. I searched for unwanted installed programs, found Speed Browser and removed it as well. After that, Firefox started normally.
I don’t know exactly if the problem came from Google Chrome or Windows 8. I suspect Windows 8 as Chrome is installed on other machines without issues and I got several other issues with Windows 8 and 8.1.