Blackout and Power Supply?

Okay, here's the situation, I built my computer 3 weeks ago, been running great and smooth

Yesterday, when I got home, my computer was off (I left it on for downloading) and was making a o.o face

I tried to turn it back on, no response, after a short while, I realized there had been a blackout, so I opened up my computer and see what's wrong, the motherboard lights were flashing, my brother said it's probably the power supply so I took it out and was preparing to take it for replacement, but then I wanted to try again while waiting for the car if it's really the power supply, so I plugged the motherboard to the PSU, and bam! It worked! (Without the bam sound) I was happy I didn't have to go and replace it.

Well... today... while I was watching some video, what do you know, another blackout... and... the whole problem is happening again... I opened the case, checked out the stuff, no good, the motherboard's lights are flashing again, I then gave the PSU a good pat on the back, and the motherboard's lights were good again...

I just want to ask if it's really the PSU that's having the problem or other stuff, and if it's the PSU, should I go back and replace it? (Don't know if they will replace it for me since it's technically working...)

Thanks!

Edit: Forgot to put specs

Processor: Intel box core 2 DUO E8400 3.00Ghz
Motherboard: ASUS P5Q3 Deluxe/Wifi-AP
Memory: OCZ DDR3 2G 1333MHz
Power supply: Antec 650 Trio
Graphics Card: Radeon 3780x2

While I would definitely agree that getting a UPS is a great idea, I'm not sure you have a problem. If you turn the PSU off with the rear switch, wait about half a minute, and turn it back on, does everything work normally? I suspect that what you are seeing is a safety feature of that PSU that keeps it shut off to protect vs. a potentially yo-yoing input power source until a person resets it.

I am sure I turned it off while I was taking it off the computer, and when I gave it a light whack in the face, the motherboard's lights stopped flashing and started working again

I will look into that before I replace it though