Last night, without any reason, my F4, F5, F6, and Esc keys stopped working. It solved itself, but shortly afterwords it did it again, and even after two reboots I cannot get them to work again. I use hotkeys all the time in Firefox and elsewhere, and these are probably my most-used keys. They're very useful and not being able to use them feels really restricting. I don't know what caused this, but I do know that both times it happened I was browsing YouTube. I don't know if that's coincidental or not, but at this point I just don't care. I just want to know what's wrong with my keys and solve the problem. This is seriously the most frustrating issue I have ever had with a computer.