I have this same problem in a HP Pavillion G6.

Problem: If I boot the machine alone, the backlight is at minumum, I can barely see the f17 (or previously the f14) logo in the middle. If I plug a vga monitor, both displays light up (get bright, no prob, can use). If I let it sleep, the wakeup happens with the lowest light level on the laptop lcd display. If I CNTRL-F2, CNTRL-F1, sometimes that solves the problem, or the FN-dim / FN-bright keys fix the issue on occasion, still investigating.

I'm still investigating, so will provide more clues as I find them.

I tried to show someone a new OS and had Fedora on the flash drive. It didn't boot to a lit screen either. I'd guess there is a bug report but check fedora first.