The simplest COM Interop app leaking memory - What I do wrong?

Question

C#

namespace TestController  
{  
    [ComVisible(true)]   
    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    public interface IController {  
        void DoSomething();
    }  

    [ComVisible(true), ClassInterface(ClassInterfaceType.None)]  
    public class ControllerImpl : IController {  
        public void DoSomething()  
        {  
            throw new NotImplementedException();  
        }  
    }
}

C++

#import "c:\prj\Controller\bin\Debug\TestController.tlb"  

using namespace TestController;  

int _tmain(int argc, _TCHAR* argv[])
{
    IControllerPtr ctrl;
    CoInitializeEx(NULL, COINIT_MULTITHREADED);
    while (true) {
        HRESULT hr = ctrl.CreateInstance(__uuidof(ControllerImpl));
        ctrl = 0;
    }
    return 0;
}

Hi all,
I need to provide access to my .NET class library from unmanaged code. Beeing totally new to the subject, I spent several days studying the COM / interop, then defined and implemented a COM accessible interface, made a test run and everything just worked, until I noticed something that seemed as a memory leak. I isolated the offending statements, but still have no clue why is the above code broken.