When I connect nodes the image starts blinking I'm trying to composite a still image, but every time I click on "Use Nodes", the image node starts acting weird/blinking. Then at the top of the toolbar it says it's trying to cancel something with the percentages fluctuating from 0 to 100 here. My render result ends up going straight white or gray.

Prior to this I was rendering an animation straight to mp4 format just so I can quickly preview it. Instead of compositing an entire image sequence I want to composite one still of it, but the nodes start having issues. This isn't the first time this has occurred.
Apparently it was due to Animation Nodes making calculations in the background.  Once I severed some of the AN connections everything went back to normal.