Ok, wasn't sure if it would do that.  Neat!

I tried to reproduce your problem and was unable.  Here's a quick
snippet of code I used.  The only difference I see (based on your
description) is that I define an interface for my .NET classes and
they'll be the default interface since I also have the ClassInterface
(ClassInterfaceType.None) attribute applied to the assembly:

using System;
using System.Collections;

namespace DispIdZero
{
    public interface IPerson
    {
        string FullName { get; set; }
    }

    public class CPerson : IPerson
    {
        private string m_Fullname = null;

        public CPerson()
        {
        }

        public string FullName
        {
            get { return m_Fullname; }
            set { m_Fullname = value; }
        }
    }

    public interface IPeople
    {
        IPerson this[string index]{ get; }
        int Count { get; }
    }

    public class CPeople : IPeople
    {
        private Hashtable m_People = new Hashtable();

        public CPeople()
        {
            IPerson p;

            p = new CPerson();
            p.FullName = "Bob Barker";
            m_People.Add("BOB", p);

            p = new CPerson();
            p.FullName = "Mike Meyers";
            m_People.Add("MIKE", p);
        }

        public IPerson this[string index]
        {
            get
            {
                return (IPerson) m_People[index];
            }
        }

        public int Count
        {
            get
            {
                return 0;
            }
        }
    }
}

Using REGASM (along with the /tlb option) I was able to get the
following VB6 code to work:

   Dim people As CPeople
   
   Set people = New CPeople
   Debug.Print people.Item("BOB").FullName
   Debug.Print people("BOB").FullName
   
   Dim op As Object
   
   Set op = New CPeople
   Debug.Print op.Item("MIKE").FullName
   Debug.Print op("MIKE").FullName

Try adding the [DispId(0)] attribute to the actual get and set methods.

---