After installing updates for Sharepoint on a SBS 2011, you may experience backup failures. The most common error is a problem with Volume Shadow Copy (error 0x800423f0 or 0x800423f3).
The error is occured because updating Sharepoint 2010 is a two-step process. Installing the updates will update the binaries, but you still manually have to update the database by running the database update command.
To determine whether you really need the update, you can run the following command from an elevated Sharepoint 2010 Management shell (available from the start menu):
PS C:> (get-spserver $env:computername).NeedsUpgrade True PS C:>
When the result returns True, the upgrade is needed.
To perform the update, you must manually run the following at an elevated command prompt each time you install Sharepoint-updates:
cd \Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\BIN PSConfig.exe -cmd upgrade -inplace b2b -force -cmd applicationcontent -install -cmd installfeatures
The update takes some time, depending on the size of the Sharepoint database. When completed, the update of Sharepoint is ready, and VSS should be able to create snapshots again.