My (lame) PC setup is owning our house's power system! O_o

This will be a little long. So bear with me.....

Well, before I got this 22 inch LCD monitor.... When playing games on my Radeon 3850 with 17 inch CRT monitor when playing games, the monitor display would start blinking and stuff (Similar to a TV that's lacking power). And at worse just sort of "shutdown" , meaning the power light in the monitor is blue but there's nothing on the screen just black, but the game continues to play normally. And pressing CTRL-ALT-DEL or the Windows menu button would the display work again. But going back to the game will usually make the symptoms go back again.

Before I thought it's the monitor, then I got lucky and my sisters husband game me his 22 inch LCD, same problem.

I got a new Radeon 4850, still same problem.

My AMD mobo broke down, so changed processor and mobo, still same thing.

And then just today, I changed the PSU. a 600W PSU, and IT STILL HAPPENS!

I'm terribly confused. Does this mean part of our house's electrical system is lacking something causing the problems?

What adds to the confusion is the issue almost NEVER happens during daytime. And my only guess it that because there's almost nothing plugged in and running during the daytime, while at night, there's lots of lights, some TVs (Our employees live here with us, so with cloth irons, radios, cellphone chargers, etc) and other appliances running.

... Or am I just getting insane? >_>