If you are developing Windows Store apps and you have multiple accounts on your laptops or PCs, you may be familiar with this problem. This happens when you try to install or deploy an app on your testing devices when the app is already deployed (by Visual Studio or PowerShell) on another user account. You will have to log in to that account to remove this app first. Sound troublesome, at least it works.
But what if you have just removed that problematic user account without uninstalling the app beforehand? I got into that weird situation when I try to test Project Timeline on a new testing account and delete the old one: I could neither deploy the app (even install from the Store) nor uninstall from the deleted user account.
Wandering around the internet, I saw several suggestions to solve this. One of them was to simply change the family name, which was not very convenient for me since I wanted to test the IAPs as well. Trying different other suggestions, I finally found a good solution: just remove the PackageRepository.edb file, and everything worked normally again. You could read the details in this blog post:
I have also come up with another solution which does not actually solve my problem but provide a way to remove all the deployed apps quickly.
http://stackoverflow.com/questions/13865930/how-to-uninstall-an-app-that-another-user-installed
Update: I have a problem now. After a while, all the Windows Store apps (except IE) on my tablet stop working: they stopped showing up when I tapped their tiles and the event viewer showed problem with their license. I am still not sure if removing the PackageRepository.edb caused the problem or my messing around earlier did. I have tried to remove the developer license, reinstall it again, remove old user accounts, add new ones, and some others, but only Store app and newly installed apps were working then. I finally have to refresh the devices. Luckily, the problem was then solved and all the Windows Store apps were keep intact.