Towards the end of last week certain apps stopped opening such as mail,news,calendar and store. I reinstalled windows 8 and all the apps that weren't working started working apart from store and apps bought from the store. When I click on the app store it just shows the loading screen then closes and doesn't provide any errors. I've tried several things already such as removing avast,checked screen resolution, running windows app store troubleshooter and I have installed all windows updates. I'm unable to do a refresh as when I try to it says some files are missing, your copy will provide these files and I put the disk in and it just says invalid media. Anyone got any suggestions to help get the app store working again.