Are you sure you want to shutdown your computer now?

Many Thanks to both abrody and network23.
I have brought it to the service center and will update what the problem was.

I had performed a hardware test and no problem was found.
I also tried to reinstall the OS but it halted at the very beginning and suddenly shutdown itself.
I tried a couple times already and it kept shutdown after a minutes at the same point, but it won't shut down during the hardware test.
I erased the disk and tried to reinstall the OS but it still shutdown at the same point. It doesn't seem to be the disk problem but something controlling the power of the machine.
Any suggestion would be appreciated.
Thanks

After checking up by the service Tech, I was told that both the power button (associating with the keypad) and logic board need replacement. I just cannot imagine how could this be possible with only using it a year, without spilling of water or ground dropping...

Many Thanks to both abrody and network23 again.

Unfortunately, on the date my MacBook Pro had problem, it was just two days beyond the one year warranty period. Since it was just too late to go for the AppleCare for repairing my gadget, I had to find ways to fix it.

Eventually It was the faults of the northbridge chip and the keyboard, after having them replaced, my beloved MacBook Pro resurrected again. I am curious why the keyboard had problem, probably it was because of the power button associating with it, but anyway my MBP works again after having them, the chip and the keyboard, replaced. I wish it just happened to my MBP, an exception only to my logic board quality, but not the other Mac lover since a breakdown just after a year is really rare for todays handheld device. I swear I have been using my MBP properly without spilling of water or dropping it on my toe.