Ok, here's what happened. About 10 minutes after i started playing Bioshock, weird lines on green points appeared on my screen. So I turned off my console, waited 5 minutes, turned it on again and there was that fucking warning screen. Only one red light (bottom right one). Error code: E74.
I searched and found that it might be my disk drive. Nop. Tried without it and it still doesn't work. Read that I should unplug everything, wait a bit, and try again. Still one fucking red light.
Now I just called Microsoft support center, and the one red light problem isn't covered by the guarantee. And it would cost me a whopping 124 $ to repair it. WTF.
Is there anyway to...you know, 'force' your console to give you three red lights ? 124$ to get a refurbished console that will break any day, no thanks.