Are you usiing AutoCAD 2012?
Configuration item <loadFromRemoteSources.../> is introduced by .NET 4. It only takes effect when the application (AutoCAD) uses .NET 4.
If you use Acad2011 or earlier, unless you force AutoCAD 2011/2010 to use .NET4 (i.e. with <supportRuntime version="v4.0" /> added to acad..exe.config), <loadFrom RemoteSources... /> will be useless.