your build errors look like an old issue of Windows regarding this Microsoft support article: http://support.microsoft.com/kb/156276/de
However, that issue should be fixed since Windows XP so with Win7 you should be fine. Is the UNC-path error also appearing if you create a normal (non-V-Play) QML project?
Another suggestion would be, to avoid any special characters in paths (so no underscores, whitespaces, etc.) and if you could try an empty V-Play project from there? Your path looks like you have installed the project on a network drive “\\USER-PC\Users\User\Qt-Projects\VPlay_Test”?
Regarding your setSource issue:
The only supported function to set the entry qml file is by using
// the default mainQmlFileName is qml/main.qml - if you want to change the entry qml file, change it here before startApplication() is called vplayApplication.setMainQmlFileName("qml/SquabyMain.qml");
If you do not want to import other QML files statically in this main.qml file, you can load them with the QML Loader element.