Unexpected call on an object that wasn't mocked

I have a test that we were running successfully in 5.4.5 but fails in 6.0.4. The failing test fails during a Form initialization reporting "Unexpected Call to IsolatorFormLoadBug.Form1.add_Load()." The form, however, was not actually mocked, so I don't understand why the error is occurring.

I have reduced the testcase down to a very small test program containing only two identical tests. If I run both, the first will pass and the second will fail. If I run only the failing case, it will pass as well.

The test code:

        public void MyTestInitialize() 
        {
            MockManager.Init();
        }
        //
        // Use TestCleanup to run code after each test has run
        // [TestCleanup()]
        public void MyTestCleanup()
        {
            MockManager.Verify();
        }
        //
        #endregion

        [TestMethod]
        public void TestMethod1()
        {
            using (RecordExpectations recorder = CreateRecorder())
            {
                MockMe mockedObject = new MockMe();

                recorder.ExpectAndReturn(mockedObject.DoSomething(), "Mocked Value");
            }

            Form1 form = new Form1();

            IsolatorFormLoadBugTest.IsolatorFormLoadBug_Form1Accessor accessor = new IsolatorFormLoadBugTest.IsolatorFormLoadBug_Form1Accessor(form);

            using (RecordExpectations recorder = CreateRecorder())
            {
                recorder.ExpectAndReturn(accessor.ShowMessageBox("", "", MessageBoxButtons.OKCancel, MessageBoxIcon.Exclamation), DialogResult.OK);
            }

            Assert.AreEqual("Mocked Value", form.Value);
        }
        [TestMethod]
        public void TestMethod2()
        {
            using (RecordExpectations recorder = CreateRecorder())
            {
                MockMe mockedObject = new MockMe();

                recorder.ExpectAndReturn(mockedObject.DoSomething(), "Next Mocked Value");
            }

            Form1 form = new Form1();

            IsolatorFormLoadBugTest.IsolatorFormLoadBug_Form1Accessor accessor = new IsolatorFormLoadBugTest.IsolatorFormLoadBug_Form1Accessor(form);

            using (RecordExpectations recorder = CreateRecorder())
            {
                recorder.ExpectAndReturn(accessor.ShowMessageBox("", "", MessageBoxButtons.OKCancel, MessageBoxIcon.Exclamation), DialogResult.OK);
            }

            Assert.AreEqual("Next Mocked Value", form.Value);
        }
        private TypeMock.RecordExpectations CreateRecorder()
        {
            RecordExpectations recorder = RecorderManager.StartRecording();
            recorder.DefaultBehavior.AutomaticFieldMocking = false;

            return recorder;
        }

The project being tested is a simple form with the following implementation:

    public partial class Form1 : Form
    {
        private String _value;

        public String Value { get { return _value; } }

        public Form1()
        {
            InitializeComponent();

            MockMe mockedObject = new MockMe();

            _value = mockedObject.DoSomething();
        }

        // This is obviously linked to the form's load event
        private void Form1_Load(object sender, EventArgs e)
        {
            ShowMessageBox("arg1", "arg2", MessageBoxButtons.OKCancel, MessageBoxIcon.Exclamation);
        }

        private DialogResult ShowMessageBox(string arg1, string arg2, MessageBoxButtons buttons, MessageBoxIcon icon)
        {
            return MessageBox.Show(arg1, arg2, buttons, icon);
        }
    }

The MockMe class is:

    public class MockMe
    {
        public string DoSomething()
        {
            return String.Empty;
        }
    }

Any idea why this is happening? I'm happy to send the entire testcase if necessary.

Thanks,
-Kevin