Excellent ideas, thank you. 
Last OS re-install was approx 16 months ago- issue was present prior install and current ( suggesting hardware?)
I usually re-image every 1.5 year, so maybe I'm due.
sfc came back clean; the buildup of C++ dist's is always a possible black hole. I'll look up those other threads to see if anything looks like it applies.
 
Memory checker is an interesting idea. Is the old Memtest comprehensive enough or is something else better suited?
Memtest and Prime95 ran well when I did last OS Re-install. 
 
Thanks again for the thoughtful and excellent suggestions.

I've had these exact graphical glitches (but not to the extent pictured). It can reliably be reproduced on my system when I hide entire folders of tracks using the Track Manager. Closing the project and reopening the project makes them go away.
 
This only manifested itself recently (AFAICT) and it was in Lexington that I really noticed it. I have not done any folder hiding since updating to Manchester so I don't know if it's persisting.
 
But yeah... I have seen exactly this. It is a graphical glitch. Restarting the program makes them go away.
 
I've had a few other little "blackout" type areas too involving things like Icons and little paramater/track number boxes that tend to go away after scrolling around and have always occasionally gotten weird vertical blackout lines.
 
The problem shown though is very new and very specific and will not go away until a restart (but clearing the picture cache may solve it as well... never tried because I jsut save and restart).
 
Cheers.

Thanks Beepster.
I'm still on Lexington ( try not to update with several projects at mid-point). So that's a common point.
My observation is slightly different:
a) restarting program doesn't eliminate the lines
b) clearing pic cache doesn't work either
c) reliably reproduced when working in "all tracks" view then isolating one track to view ( ie hiding all others including folders)
Thanks again for the input.