No need to uninstall or download the setup from battle.net if you get this error. Just delete file and run the launcher again.
If you get the same error, download the file from:http://blizzard.vo.llnwd.net/o16/content/d3-pod-retail/NA/8370.direct/Updates/d3-0-9558-Win-final.MPQAnd save in your "Diablo III\Updates" folder before starting the launcher again.
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