To repair Application Support file permissions:

  1. Open Terminal, located in /Applications/Utilities.
  2. Type or copy and paste the following command for the affected application:
    sudo chmod 0754 ~/Library/Application\ Support/Battle.net
  3. Press Return.

If your system is not in English, you might need to translate Library/Application appropriately.

Note: You may be prompted for your administrator password when using the commands above. You may not see characters appear when typing, though it will accept your password.