Your interference doesn't seem like moiré to me, it must be from a different source. Have you tried better cables/moving away other electrical equipment?
To see what moiré looks like; if you have Windows 98/ME Select Start Menu, Shutdown but don'r actually shut down the computer... from the grey pattern generated, most monitors will exhibit moiré. If yours doesn't [you will see an odd patter if it does], adjust the moiré controls on the monitor (remembering the original value; although reducing moiré compensation will improve your monitor's focus considerably).
Hope this helps