I have recently setup a server Windows 2012 with Citrix Xenapp as an application server with published desktops for my users. Randomly when users are logged on and click on the Windows Start Menu, the screen with all the tiles is just blue and the tiles are all gone. They can bring up the Side bar to search for an app and launch but the tiles are missing. They eventually appear but not sure what cause them to disappear or re-appear. Any insights would be greatly appreciated.