Sounds like interference of some type but could be driver related as well.
Check that your cables from monitor to display adapter are secure. Check
around for things like speakers, phones, other electronics and try
distancing them away from the monitor a bit. (Example: A friend had a lamp
with a dimmer switch on same circuit as monitor. Moved plug for lamp to
another outlet - no more display problems.)
May also want to check your display and refresh settings. If pushing the
limits of the hardware, adjust settings down a bit to see if performance
improves.
