Fix #1

Go to Control Panel > Administrative Tools > Services

Scroll down and find “Secondary Logon”

Right Click > Properties

Change it from ‘Disabled’ to ‘Automatic’

Run your Diablo 3 setup as administrator and it should quickly go through Updating Setup Files and bring you to an install screen. Congratulations, your game now (hopefully) works! If this solved your issue, spread it around.

Fix #2

Right click on the Diablo 3 setup file you downloaded via the Blizzard Downloader

Select Properties > Compatibility > Check Run this in Compatibility Mode for… > Choose Windows XP (Service Pack 3) (Note: Does not work on Vista.)

Right Click the Icon, Run as Administrator.



Fix #3

Delete your C:\ProgramData\Battle.net folder.

Delete your C:\ProgramData\Blizzard Entertainment\Battle.net Cache folder.

Run the Downloader again, as administrator, and see if it gets past the “Updating Setup Files” window. If not, see Fix #1.



Fix #4 (Thanks Ron!)

This one worked for me: try and find the agent application in the battle.net folder (for example C:\Documents and Settings\All Users\Application Data\battle.net\Agent). Start the agent application manually and after that start Diablo III setup file in your Diablo-III-8370-enGB-Installer folder. Good luck!

Fix #4a – Clarification for Fix 4 by GarytheOak

1. Run the diablo insall thing… let it get stuck.
2. Close it, and ctrl+alt+delete and end the “Agent” process.
3. Go to C/programdata/battle.net/agent and run the “Agent” executable
4. Run the diablo install thing
5. WAIT! it will get stuck for a min or so and then work

Fix #5 (Thanks SCH)

NOTE: This Fix is experimental. Many are reporting success. Proceed with Fix #5 at your own risk,

“I followed all of the posted fixes and none of them were working for me. An user on the battle.net forums posted his version of the C:\ProgramData\Battle.Net folder and uploaded it. All you have to do is replace his version with your old version, and hopefully everything should work (as it did for me).” -SCH from comments

http://www.gamefront.com/files/21699449/D3...e.net+Files.zip

Fix #5 Additional Notes: If you get a decryption error it means you probably didn’t finish the download. Check the folder you downloaded your files into for any that say .PART as the presence of a .PART file means you haven’t finished downloading. decryption error might also indicate a corrupt download. Run the downloader in the same directly you chose originally and it should fix the files automatically and/or finish downloading.

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Im having the same problem b4, n somehow Fix#5 solved the problem =)

Credits: http://www.keenandgraev.com