Brightness Key Issues

I've had this issue for a while and it's really frustrating. Fairly often when I'm using my Inspiron 5758 computer, I'll hit the F11 or F12 keys to adjust the brightness and the screen will just go black. Then I have to wait a minute or so before pressing the power button and the welcome/log in screen will pop up.

To prevent unnecessary questions:

-Yes, I am sure I am not accidentally dimming the screen