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):