Volume Shadow Copy Service (VSS) is a Windows subsystem, and we do not bear any responsibility for its functioning. In case of any problems with it, please request technical support from Microsoft directly. Below are the advices that can be helpful.
To backup open/locked files, DoubleSafety must be run by a member of the Administrators or Backup Operators group. Under Windows Vista, DoubleSafety must be run under elevated privileges.
Supported operating environment
Open/locked files can be backed up only under Windows XP or newer operating systems – provided that the data is copied from a local NTFS file system. FAT32 is supported on internal drives only, on the term that an NTFS partition is also available.
Keep your Windows current
To ensure hassle-free operation, make sure you have all latest Windows updates and patches applied. Check your operating system's current status and apply the latest updates via Start -> All Programs -> Windows Update.
Possible sources of interference
The proper functioning of VSS can be prevented by running anti-virus or disk imaging software. Check out your applications’ websites to find out whether or not they can cause any problems to using VSS.