Kuan, once had a similar problem myself. All outlets on the interior walls and ceiling fixtures would go out on my second floor for no apparent reason. House is over 25 yrs old. Turned out to be a wall outlet with loose contacts that affected everything wired down the line behind it. Point being it looked major, turned out to be $2.00 minor. Be careful either way. Electrical is the one thing I will not touch at my place unless the whole house is "dead". Spouse is the one with 1,000,000 policy and even then, I can't be in the same room and so sneak to turn everything off. Shocked myself before pushing a thermostat back into a running dryer(minor zap) and grabbing a sparking coil wire on a Toyota(major zap, arm hurt for hours!). Do not every want to be situation where it gets me and I don't live to know it!!