NP530U4C very hot with screen down...

Something very strange happened to me today...
I was installing a game in my laptop, and left it alone to its business: put the screen down (nothing happens when I put the screen down), the selected power "preset" was Samsung Optimized, it was connected to electricity, charging. After maybe 30-45 minutes, got back to the notebook, it was still on and the HDD light was flashing. When I lifted the screen, the fan started working imediatly, very noisy, and when I saw the temperature, I couldn't believe: more than 70ºC!!! It never reached this temperature, even when playing heavy games. I reallized that whith the screen down (and off) maybe the fans aren't supposed to work (???), because when I lifted it up, they started working immediatly. In this power setting, I have "Suspend" not set (it won't suspend automatically), only when in battery, and the CPU cooling option is set to passive in battery, and active when connected to power.
I thik I remember a user complainning about the same thing, but I think he said is notebook was trying to suspend. Mine wasn't, it wasn't set to suspend...
Does anyone know what could have happened here...?
It could've been hotter, if I haven't left it on my notebook cooler...