KB2919355 problem information
It is well reported that problems can be experienced during the installation of KB2919355 for Windows 8.1. This is a 'must have' update as it will be a pre-requisite for installing future updates.
I was one of the unlucky ones that experienced error 80073712 when attempting to install this update. The issue seems to be a conflict with this update and other updates which are already installed. The way I got around this which may be of interest was:
I rolled back the OS so that the last updates I had installed were from March. I then downloaded from the Microsoft download site (rather than using 'Update Windows') the update KB2919355 together with updates KB2919442, KB29329046, KB2937592, KB2938439 and KB2934018. I then installed then in the order:
rebooting after each install when required.
I then used 'Update Windows' to install the remaining updates. This process enabled me to install all the updates successfully.
All advice is offered in good faith only. You are ultimately responsible for effects of your programs and the integrity of the machines they run on.