Occasionally after turning my keyboard brightness all the way down to 0 manually (Which I do sometimes at night if I need to leave the machine running while it processes something) it won't allow me to turn it back on.
It gives me this symbol when I try. It usually lasts until I reboot. But is not easy to reproduce as it does not always happen.
Something tells me this is unanswerable, but I was hoping someone else might have discovered this problem too.
2010 2.4GHz MacBook Pro.