I had this problem too. Contacted Ashley and he suggested me to reinstall everything from scratch. I did and it works now.
You should be careful with the folders too, I think the new C2 versions do not use the "C:\Program Files\NodeWebkitForC2" folder but "C:\Program Files\NWForC2" or something. Basically what I did was
1. Uninstall C2 completely (with all the plugins that will remain in the folder)
2. Download and install latest version (and copy over plugins)
3. Install LATEST NW.js
4. Find the directory it has been installed to (probably "C:\Program Files\NWForC2")
5. Delete everything in the directory
6. Copy over NodeWebkit 10.5
I also asked — for his NodeWebkit folder and used it, but it should be the same.