From what you are telling me it is a hardware problem. One thing i'm sure of BIOS UPDATE HAS NOTHING TO DO WITH IT 
If your BIOS was broken or update was unsuccessful you would not be able BOOT (into anything), but POWERING UP (turning on)
is a generic function and has nothing to do with software.

Of course i can't be 100% correct (since i don't physically see your unit), but it 100% sounds like DYING CAPACITORS on your motherboard.
It usually happens when capacitors come to an end of their lifespan (from 5 to 25+ years ), but since your laptop is new, they should be just DEFECTIVE.
Once it starts it's almost always a progressing process (on ANY motherboards).

CAPACITORS are like temporary rechargeable batteries. They collect electricity and stabilize the voltages when needed (very primitive way to put it )
When they go bad, it takes several times for the user to push the power button (it's when capacitors get that FIRST CHARGE) to give them
enough charge to start your motherboard. Otherwise your motherboard "thinks" that there is "not enough electricity" to start up.

If i'm right (and i THINK i am) then it is going to take more and more button pushes to turn your notebook on with time and some day it will stop turning on at all.

SOLUTION

On desktop motherboards it's an easy fix, you just replace the capacitors. They are visible (the BAD ones), cheap and
easy to replace. But since you got a notebook it equals a repair with special equipment or MOTHERBOARD REPLACEMENT.
Good thing you got warranty. So let ASUS deal with it (the sooner you do it the faster you'll stop worrying about it )

Good luck 

---

Added on December 11, 2011, 4:04 pm

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Peace.

want to ask ::

N45SF now is selling with 7200 rpm HDD or still 5400 rpm??

we need more ppl. XD