Q: MacBook Air & External Monitor Screen Flickering

HI all.  I searched the forums and found similar issues, but nothing exactly like what I'm seeing.  My mid-2014 MacBook

Air and the Dell p2414h monitor I have it hooked up to will, occasionally, start flickering.  It's not turning on and off like some of the other examples, but just flashing enough to be annoying.  Here's a video

of it, slowed down to 120fps, that illustrates the problem:

http://www.youtube.com/watch?v=NY9Ct6BBnJI&sns=em

I thought it might be the p2414h, but now that I see the Mac screen flashing too I'm not so sure.

Has anyone seen this before?

Thanks!

Mark