Error: The file "C:\Program Files (x86)\Diablo III\Updates\d3-0-9558-Win-final.MPQ" appears to be corrupt. You may need to download this file again.
1. Deleted the MPQ file.
2. Downloaded the new game client (30mbs).
3. Ran the new game client (30mbs) as administer.
Thanks to MrMocket for the help in solving this.
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.
Thanks to Barthus for this ^^^^^^