From the Diva's blog.
A new Volume Shadow Copy Service update is now available that fixes various Volume Shadow Copy Service problems in Windows Server 2003:
Availability of a Volume Shadow Copy Service (VSS) hotfix rollup package for Windows Server 2003 to resolve some VSS snapshot issues:
are needed for the server and an update is available to optimize the way that the Shadow Copy Client accesses shadow copies in Windows Server 2003 and in Windows XP:
is needed for the workstation
But if you have Windows Server SP2 installed, you have KB913648 already installed.