For future googlers 
:
I got this same error message, and through a process of elimination I discovered that the problem was due to an image asset in the project that was missing from my local filesystem (after copying the project folder - because the image was actually outside the project folder). Why this simple error caused Encore to crash is beyond me, but simply removing the image allowed me to open the project on my new computer, as did copying the file to the project folder and using "replace asset" to link it to the copy in the project folder.