Updates do fail occassionally but will normally try again later. The error message seems to mean "No signature was present in the subject" but looking at the WindowsUpdate.log in the Windows folder, or maybe the ReportingEvents.log in the Windows\SoftwareDistribution folder would give more clues. A good internet connection seems to be fairly important with Windows Update.
If you want to try to install it manually, go to the Microsoft Update Catalog and download and install manually. Make sure you get the correct version.