Windows Update Error Code 84BE0BCE, now this doesn't say anything useful so to the Google-O-Matic we go.
Many will suggest to install the SP3 manually, so after downloading the file and running the installer I got this:
Not very useful as well...
Turns out there's a command line installation option with this (I never would have guessed I never do anything with SQL).
The option is to skip the cluster check like this:
C:\Temp\SQLServer2008R2SP3-KB2979597-x64-ENU.exe :\Setup /SkipRules=Cluster_IsOnlineIfClustered /action=patch
The same goes for KB3045316:
SQLServer2008R2-KB3045316-x64.exe :\Setup /SkipRules=Cluster_IsOnlineIfClustered /action=patch
And then you can install the SP3 without the error in the first screenshot because the cluster check rule is skipped.