I'll wait for the definitions update...but, apologies if this is a silly question, is it okay to be online without the failed Windows Update? (All the others installed successfully.)
The update can be re-installed.
If it fails to show you can always "trick" Windows into rescanning for updates.
Run -> type: Services.msc -> Stop: Windows Update service -> delete the update folder: C:\Windows\SoftwareDistribution -> Start: Windows Update service.
Recheck for update as always.
PS: You will loose your update history