On a computer that is running Windows Vista Service Pack 1 or Windows Server 2008, when an application tries to obtain an exclusive lock to a volume, the attempt is unsuccessful. Additionally, you may receive the following error message:
Access is denied
For example, when a backup application restores data on a volume, the application may try to obtain an exclusive lock to the volume. In this case, the restore operation is unsuccessful.
This problem typically occurs after the system runs for several hours. When this problem occurs, you may discover that the System process is holding handles to some volumes.
Note: This problem does not occur on a computer that is running Windows Vista without Service Pack 1.