Difficulty verifying private methods

Hi,

I am writing a very simple test to verify that a private method is called when a public when is invoked.

Below is a sample that illustrates this.

using System;
using NUnit.Framework;
using NUnit.Framework.SyntaxHelpers;
using TypeMock;
using TypeMock.ArrangeActAssert;

namespace UnitTests
{
    public abstract class Foo
    {
        public void DoIt()
        {
            privateDoIt();
        }

        protected void privateDoIt()
        {
        }
    }

    [TestFixture]
    public class FooFixture
    {
        [SetUp]
        [Test, Isolated]
        public void TestDoIt()
        {
            var f = Isolate.Fake.Instance<Foo>(Members.CallOriginal);
            f.DoIt();

            Isolate.Verify.NonPublic.WasCalled(f, "privateDoIt");

        }

    }
}

It seems simple enough but each time I run this test I unexpectedly get the following error:

TypeMock Verification: Method Mock0000Foo.privateDoIt() was expected but was not called

After toying with it I discovered that if I change the method accessibility from private to protected it works the way I would expect, that is to say it succeeds.

Can someone tell me what I might be doing incorrect?

I am using Isolator v5.3.0 on VS2008 with TestDriven.NET 2.19.2409.

Thanks,

Darin