Well, too many words and no concrete recommendations, as usual. i assume original poster uses HDMI cable connection to the monitor. HDMI is particularly sensitive to impulse interferences as it uses weak signals (~800mV) at rather high frequency. Especially with a cheap cable having thin shielding. My advice is just to ignore this (I had this too when connecting my monitor to a Blu-Ray player with a long cable) or to use a better cable, with a thicker shield and preferably interference-suppressing ferrite core molded in the middle. Ferrite core breaks ground loops at high frequency, working as a transformer, and so makes the life in that respect better. You may try to clip a ferrite core / tube on the cable yourself if you have a spare from some other equipment.