Google in Crisis: "This site may harm your computer"

Every search result on Google just now seems to flagged with their "This site may harm your computer" warning. Even Google itself: oops! Screenshot taken 3pm, 31/01/2009:

Update 6.30pm: BBC report: 'Human error' hits Google search
Update, 1.00pm, 01/02/2009: Official Google Blog: "This site may harm your computer" on every search result?!?!