Monitor flickering problem

I have a monitor here that started flickering pretty much out of nowhere. The screen kind of shakes or vibrates. The most recent change was installing McAfee anti-virus, but that was a number of days ago. I lowered the monitor refresh rate to 60 Hz, as it is readable without eye agitation, but it would be nice to be able to bump that back up again.

Is it a video card problem or a monitor problem (or something else completely?)

 

Do you have any electrical sources around it? Such as a fan or a light, could even be something in the next room if you have this up against a shared wall.

 

a way to test it is get another monitor in there and put that in and leave it back at the orignal rate were it was flickering ...if it still has the same problem ..then it is most likelly a vid card issue.

 

Hey, alright, that fixed it. It was a fan. That was easy. Thanks!