So another management console installation problem today. This time SQL.

The error I got:
ERROR: Runtime error: This method explicitly uses CAS policy, which has been obsoleted by the .NET Framework. In order to enable CAS policy for compatibility reasons, please use the NetFx40_LegacySecurityPolicy configuration switch. Please see http://go.microsoft.com/fwlink/?LinkID=155570 for more information.

Solution:

• Backup machine.config, enterprisesec.config, enterprisesec.config.cch, security.config & security.config.cch in C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Config
• Edit C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Config\machine.config
  • Replace <runtime /> with <runtime> <NetFx40_LegacySecurityPolicy enabled=”true”/> </runtime>
•  Navigate to C:\Windows\Microsoft.NET\Framework64\v2.0.50727
  • Run caspol.exe -all -reset
• A security.config and security.config.cch will be created in C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Config
  • Copy these files to C:\Windows\Microsoft.NET\Framework64\v2.0.50727\Config and C:\Windows\Microsoft.NET\Framework\v2.0.50727\Config
• Execute SQL Setup
• Restore original files in C:\Windows\Microsoft.NET\Framework64\v4.0.30319\Config\machine.config

This worked for me.  Let me know if it works for you!