If everything was working, then it suddenly stopped, it seems unlikely to me that it would be a C2 or NW.js problem. More likely it's an OS/Antivirus/GPU change that has triggered it.
What happens when you run NW.js in debug?
Maybe try an export with a keyboard action to show the devtools - might get some info from that.
Have you got access to another machine that you could maybe install the release from today, along with today's release of NW.js? NB/ both available from HERE.
Or even try to install standalone r217 in a new folder with the new NW,js.