Does unclean power cause graphic problems?

It is more likely the power supply as the power supply converts the AC to DC. I doubt the unclean AC power much affects the DC output. It's possible the power supply is producing a slightly under or over current. A second option is that the power supply isn't supplying (or can't) enough power to perfectly please the video card & monitor while also charging the battery. Try it again with the battery fully charged. I don't think a power cleaning strip will hurt but if you buy it, just save the receipt and take it back if it doesn't help.