Failed to add extra items to the selection tree error for System State backup. (86460)

From the Binary Log we can see that the backup job for System State fails with the following error:

Job ID 131 - Error 2011/12/13 21:00:04 131 Data Plugin CHARON Failed to add extra items to the selection tree

I checked Case Environment details from the case and could see that the customer has installed NVBU 8.2.1 on Windows 2008 R2 Server and Client.
As you can see from the NVBU Compatibility Guide that this is not supported:

https://support.quest.com/Search/SearchDocumentation.aspx?dsNav=Rpp:25,Ro:0,Ns:P_DateLastModifiedSortable%7c101%7c-1%7c,Nrc:id-11%7cid-5%7cid-58,Nea:False,N:268446836,Nr:AND%28OR%2835%2c8%2c43%2c59%29%2cP_SecurityRole%3aEXTERNAL%29&Dt=NetVault+Backup&SKB=1

For Windows 2008 R2 you need a minimum of NVBU 8.5 on the NetVault Server and Clients. We now have NVBU 8.6.1 and can be downloaded from our website:

https://support.quest.com/NetVault Backup

Please check the Release Notes from the first link to check which items have been fixed and items that are still outstanding.
Have you just installed NVBU 8.2.1 recently? If you have I would advise to uninstall NetVault, reboot, install NVBU 8.6.1 from fresh and lastly reboot again on the NetVault Server and Windows 2008 R2 Clients so that you have a valid installation. Further uninstall information is in the NetVault Installation Upgrade Guide.
Upgrading from an unsupported version may cause problems later on.
Customer had performed fresh installations on the Server and Client and the backups are now working.