Sigh! Seems to happen with all the Microsoft Silverlight updates.
And on my home PC (Windows 7 Professional), but not my laptop (Windows 7 Home Premium) which resolved itself after a Windows restart and subsequent try.
The following link discovered using Google referencing KB2690729 renders the illustrated page:
This effectively renders the automatic Windows update "KB2690729" redundant. After the installation, once Windows has updated its lists, etc. the update is no longer selected by the automatic update utility.
The update history will continue to display the last failed incident without a successful subsequent update. This is no cause for concern as it is now irrelevant in view of the overriding new installation.
See "Control Panel\All Control Panel Items\Windows Update\View update history" for details.