New release of the Windows 8 SDK?
On submitting an update for one of my apps i just got prompted to install an updated SDK – looks as though this is mandatory for certification.
NB This is quite a large download at 568.6 MB
Looks as though it isn’t mandatory as after kicking off the download, I selected ‘next’ in the first dialog above and managed to finish the certification submittal.
Note: A reboot is required after installing the update: