C# – Crystal Report Error. Failed to open the connection

Possibly a security precaution. You could try adding a new administrator account:

mysql> CREATE USER 'monty'@'localhost' IDENTIFIED BY 'some_pass';
mysql> GRANT ALL PRIVILEGES ON *.* TO 'monty'@'localhost'
    ->     WITH GRANT OPTION;
mysql> CREATE USER 'monty'@'%' IDENTIFIED BY 'some_pass';
mysql> GRANT ALL PRIVILEGES ON *.* TO 'monty'@'%'
    ->     WITH GRANT OPTION;

Although as Pascal and others have noted it's not a great idea to have a user with this kind of access open to any IP. If you need an administrative user, use root, and leave it on localhost. For any other action specify exactly the privileges you need and limit the accessibility of the user as Pascal has suggest below.

Edit:

From the MySQL FAQ:

If you cannot figure out why you get Access denied, remove from the user table all entries that have Host values containing wildcards (entries that contain '%' or '_' characters). A very common error is to insert a new entry with Host='%' and User='some_user', thinking that this allows you to specify localhost to connect from the same machine. The reason that this does not work is that the default privileges include an entry with Host='localhost' and User=''. Because that entry has a Host value 'localhost' that is more specific than '%', it is used in preference to the new entry when connecting from localhost! The correct procedure is to insert a second entry with Host='localhost' and User='some_user', or to delete the entry with Host='localhost' and User=''. After deleting the entry, remember to issue a FLUSH PRIVILEGES statement to reload the grant tables. See also Section 5.4.4, “Access Control, Stage 1: Connection Verification”.

I think one can end up in this position with older versions of mysql already installed. I had the same problem and none of the above solutions worked for me. I fixed it thus:

Used brew's remove & cleanup commands, unloaded the launchctl script, then deleted the mysql directory in /usr/local/var, deleted my existing /etc/my.cnf (leave that one up to you, should it apply) and launchctl plist

Updated the string for the plist. Note also your alternate security script directory will be based on which version of MySQL you are installing.

Step-by-step:

brew remove mysql

brew cleanup

launchctl unload -w ~/Library/LaunchAgents/homebrew.mxcl.mysql.plist

rm ~/Library/LaunchAgents/homebrew.mxcl.mysql.plist

sudo rm -rf /usr/local/var/mysql

I then started from scratch:

1. installed mysql with brew install mysql

2. ran the commands brew suggested: (see note: below)

   unset TMPDIR
   
   mysql_install_db --verbose --user=`whoami` --basedir="$(brew --prefix mysql)" --datadir=/usr/local/var/mysql --tmpdir=/tmp
   

3. Start mysql with mysql.server start command, to be able to log on it

4. Used the alternate security script:

   /usr/local/Cellar/mysql/5.5.10/bin/mysql_secure_installation
   

5. Followed the launchctl section from the brew package script output such as,

   #start
   launchctl load -w ~/Library/LaunchAgents/homebrew.mxcl.mysql.plist
   
   #stop
   launchctl unload -w ~/Library/LaunchAgents/homebrew.mxcl.mysql.plist
   

Note: the --force bit on brew cleanup will also cleanup outdated kegs, think it's a new-ish homebrew feature.

Note the second: a commenter says step 2 is not required. I don't want to test it, so YMMV!