Security Update for Windows XP (KB917344) & Cumulative Security Update for Internet Explorer for Windows XP (KB916281) both failed today - as they have done since the beginning of June. The IE updates have been failing since Cumulative Security Update for Internet Explorer for Windows XP (KB905915) in February 2006 (perhaps before - the log only goes back that far.
My version of Windows XP SP2 has been validated by all your tools as Genuine - as it should be.