Windows 2008 System State backup fails on System files - "Failed to add extra items to the select (4042589)

When performing a System State backup on Windows 2008, the job fails with the following log messages:

Error 2009/02/02 17:11:40 34 Data Plugin NETVAULT Failed to add extra items to the selection tree
Severe Error 2009/02/02 17:11:40 34 Data Plugin NETVAULT Failed to prepare the selection tree and backup options

The File System trace shows problems with WFP (Windows Files Protector) files, also known as WRP (Windows Resource Protector) on Windows 2008:

0 SSFILES :2552 2 0 135456 Failed to add WFP files when creating files tree
0 NVFSWIN :2552 1001 0 135456 Failed to get system files tree from ss module : 'Failed to add protected files to the backup tree'
0 NVFSWIN :2552 1044 0 135456 Failed to add System State system files to extra items tree
0 HBBACKUP:2552 118 0 135456 Failed to get extra sub level backup items

The Windows Event Logs would in some cases show:
Cryptographic Services Failed while processing the OnIdentity() call in the System Writer Object.
Details: AddCoreCsiFiles: BeginFileEnumeration()Failed
SystemError: Access is Denied.