I have a strange problem with my HP Pavilion laptop. The brightness of screen goes randomly zero but everything else work perfect. increasing brightness of screen doesn't change anything. If you turn an external light in front of laptop display, I can see the content. I checked in Both Windows(7) and Linux (Ubuntu) the same problem happens. I need to logout or change resolution to be able to use the computer again.
I guess it is a hardware defect. What is your idea?