A consensus is emerging in Windows 8 forums around the net that Office 2003 as a suite or individuals apps therefrom break Windows 8's Update.
Diagnosis of the initial reports attributed the failure to Windows 8 x64 [RTM] upgrades over Windows 7 x64 that had Office 2003 installed.
My experience, however, was with a 'clean' install of Windows 8 Pro [via TechNet] and the same result is being confirmed in other forums now.
So far there is no indication of Office 2003 (SP3) applications not functioning normally in 8. My early testing of Outlook, Excel, and Word have them working flawlessly — even with a highly reduced set of macros from Woody Leonard's legendary WOPR 2003!
There is no comprehensive fix at this time for the Windows Update problem. It is conjectured that this may be a 'Certificates' issue with Office 2003. That would necessitate a Hotfix from Microsoft for software that passes out of active support next year. Disabling updates for 'other Microsoft products' will restore Windows 8 ONLY updating.
Some will simply switch / upgrade to Office 2010 — which I have learned to accept then appreciate — but many folks remain alienated by THE RIBBON, not to mention the cost and loss of certain macros, older add-ins, reduced customizability, etc; or wait for Office 2013.
Interesting it will be to see whether Microsoft (Office Division) comes through for its installed-user base on this one.