I've traced a problem with XMLHttpRequest on PhoneGap for Windows Phone 8 to the debug setting on PhoneGap Build (turning it on causes XHR to silently fail). Unfortunately, the PhoneGap Build component for Dreamweaver always turns debugging on. It appears to take no ntoice of the ProjectSettings file that is created in the project folder (I have set "debug":false with no effect) and turning debugging off on the build.phonegap.com site also has no effect on the next build initiated by Dreamweaver.
The Dreamweaver PhoneGap component needs to be adjusted to take notice of the ProjectSettings for debug and to update these according to the actual settings on the web site. Alternatively, expose the debug setting in the PhoneGap build panel.
I have had to abandon DreamWeaver for Windows Phone builds altogether.
