Apple Breaks Multiple App Store Account Updates – 'You can not update this software since you have not owned the major version of this software'

Boom! Apple broke App Store accounts for many users with multiple accounts recently. On checking for updates and clicking the helpful 'Download All Free Updates' button, iTunes rather unhelpfully states: 'You can not update this software since you have not owned the major version of this software'. Whether this is a bug (which we hope) [...:]