I found this thread : Probem using SenchaTouch 2
Sadly it can't help me on Mac OS.
I have the exact same problem. My App.json cause an Error 404.
I'm using apachectl (terminal in mac OS) and I don't know how to add MIME to it to make everything work on Chrome.
I'm also wondering why it works on Safari but not on Chrome.
The error I am getting :
XMLHttpRequest cannot load file://localhost/Users/guillaumecharron/Sites/CarboZero/app.json. Cross origin requests are only supported for HTTP. index.html:1
Uncaught Error: NETWORK_ERR: XMLHttpRequest Exception 101