Indicator light blinks fast on macbook

What does it mean when the light on the front of my macbook starts flashing fast. not the normal sleep fading in and out kind of flash, it's more like a "something is severely wrong" flash.

Right before it happens, my computer makes the optical drive noises as if it's going to sleep, or something, but doesn't. it seems as though it just turns itself off... I can't get it to come back, no pressing the power button, no key presses, nothing.

I have to hard restart the machine by holding down the power button for a few seconds.

Any ideas?

Well, I've found that my problem of the computer randomly turning off/sleeping is independent from any software issues, as it only happens when I pick up the computer, and put a normal amount of pressure under the left hand side of the machine, which is exactly where the cpu/graphics chips are located.

Back to Apple, for a second logic board.... GAH!!!! AND another month without a f*cking apple, back to F*cking windows pc's....