An attempt to add a new device to USB Devices White List in Group Policy Editor fails with the The Group Policy snapin was unable to save changes due to the following error: The process cannot access the file because it is being used by another process. error.
By some reasons MMC cannot write to SYSVOL directory from the domain controller, which results in this problem.
The issue can be caused by a backup software on DC, removing it may eliminate the problem.
- Export DeviceLock Service settings from your existing GPO or connect to any DeviceLock client with DeviceLock Management Console -> right click DeviceLock Service node -> Save Service Settings.-> press OK;
- Delete the GPO you can not change;
- Create a new GPO and import the previously saved DeviceLock Service Settings file;
- Add the devices to USB Devices White List in the new GPO.