SBS 2011 Backup Failure - A Volume Shadow Copy Service operation failed. Unknown error (0x800423f0)

I was configuring SBS backup on an SBS 2011 machine to a 2 TB external hard drive. But I got this error on the first backup:

SBS 2011 Backup Failures - A Volume Shadow Copy Service operation failed. Unknown error (0x800423f0)

After some quick research, I found that in some of the updates installed, there was a Sharepoint update that had downloaded, but needed to be manually installed. That's pretty lame, but whatever.

The method of updating Sharepoint properly is discussed here:

http://blogs.technet.com/b/sbs/archive/2011/05/24/you-must-manually-run-psconfig-after-installing-sharepoint-2010-patches.aspx

In essence, it's just go to an administrative command prompt. Go to this folder:

C:\Program Files\Common Files\Microsoft Shared\Web Server Extensions\14\BIN

and run this command:

PSConfig.exe -cmd upgrade -inplace b2b -force -cmd applicationcontent -install -cmd installfeatures