If your lamp is flickering, it sounds like electrical. Is the lamp on the same circuit as your PC? Might be a faulty breaker... that spazzes out a little when a load is put on it. Do the lights flicker when your AC, or refrigerator kicks on? If so, it might be more than just a single breaker.
How much do you have plugged into that line? Depending on where you are, code will determine how many devices you are supposed to be able to hook up on each breaker (usually around 12 or so for a 15 amp breaker)... actually based on load current... not supposed to exceed 80% of the breakers rating. Do you know if the amperage of the breaker you are on? If it is overloaded... it can cause that brownout effect at times.
You might try resetting the breaker (make sure all connected devices are off first, of course). Sometime they develop a weak connection, and a reset will correct it. If not, you may need change out the breaker (get a electrician if you are not comfortable with it)
If it was PSU.. the symptoms would be limited to your PC... unless you were getting a serious short, and you would notice that... Edited by cgipson1 - 3/7/14 at 9:30pm