If you use roaming profiles on your Windows-based network, you may have experienced issues caused by registry hive corruption. This can happen when poorly-designed applications try and keep registry hives open after the user logs off from the network. An easy way to tell that this is occurring is to scan the Application log on the user's machine for event IDs 1517 and 1524, which indicate that the user profile is not unloading successfully during logoff.
To resolve this problem, obtain the User Profile Hive Cleanup Service add-on from the Microsoft Download Center. This service runs in the background and looks for users who have logged off but still have their user profile hives loaded. When it finds such users, it determines which applications have open handles to the registry and forces these handles to be released. You can download this utility here.