The new framework and infrastructure around apps in Windows 8 brings some new challenges to deal with. To start with you cannot turn off User Account Control if you want to use the modern apps in Windows 8, but there are more going on behind the scenes that are essential to the working of Windows Store Apps.
When a problem do occur Microsoft provide a nifty little troubleshooter tool for Windows Store Apps, download and run the tool from:
http://go.microsoft.com/fwlink/?LinkId=271185