There is a thread in the Bug-Reports with something similar, but not exactly the same problem and the solution doesn't work for me.
The problem is, if I export to NWjs or start the preview in Construct it only works once. After closing the app, all nw.js tasks I can see in the Task-Manger get closed too. But if I start the preview or execute the exported app a second time, two tasks appear in the Task-Manager and nothing happens. I have to rename the project in Construct or delete the folder with the name of the app in <username>/AppDate/local and kill the tasks, then it works once again.
This is with the exported 32 Bit version, the 64 Bit version crashes immediately.
I use Windows 7 home premium 64 Bit with Construct 221 and NW.js 0.13 Beta4. The question is, I am the only one with this problem? Could someone test if he/she has the same problem?
Edit: I think I found the culprit. I seemed my old Node.js install had caused problems. After uninstall node.js, nw.js and construct and reinstall construct and nw.js it now works.