ESB Error: Could not load file or assembly ‘Configuration, Version…’ when you select the button to choose a user account

An error occurs when trying to use the ESB Configuration Tool. When you press the eclipse button for the user account on either the Core Web Services or Exception Web Services configuration you get the following error:

Fix:

Close the Configuration Tool. Open ESBConfigurationTool.exe.config and change the "ExceptionUserAccount" value for Exception Web Services and "CoreUserAccount" for Core Web Services . Save the config file and open the configuration tool. The values will be pre-populated.