Security Update for SQL Server 2012 Service Pack 2 (KB3045321)
Date: 25/07/2015 13:26
Installation status: failed
Error details: Code 84BC7381

I've re-run de update a couple of times with the same (lack of) result.

Has anyone a clue?

Thanks in ad

Check this: https://technet.microsoft.com/library/security/MS15-058#ID0EYIAC

Are you on a supported major/minor version of SQL ?
Are you on GDR or QFE servicing branch of SQL?
Are you on a supported OS?

Because this topic is specific to servicing SQL, you may check the dedicated SQL forums on MSDN (rather than this Windows 8.1 forum):
https://social.msdn.microsoft.com/Forums/en-US/home?category=sqlserver

Thanks Don. The Technet link allowed me to install the update 'manually', i.e. without using Windows Update.

That worked fine. So I presume that the issue is in Windows Update. Anyway it is olved as far as I am concerned.

Alan