I'm using Windows 7 64-bit Ultimate edition

Here is my program code for C#:

using System;
using System.Collections;
using System.Windows.Forms;
using Sony.Vegas;
using System.Drawing;

namespace Example
{
    public class Example : ICustomCommandModule
    {
        protected Vegas myVegas = null;//Dockable edition

        public void InitializeModule(Vegas vegas)
        {
            myVegas = vegas; //Dockable edition
        }

        CustomCommand myViewCommand = new CustomCommand(CommandCategory.View, "myViewCommand");

        public ICollection GetCustomCommands()
        {
            myViewCommand.DisplayName = "Hello World View";
            myViewCommand.Invoked += this.HandleInvoked;
            myViewCommand.MenuPopup += this.HandleMenuPopup;
            return new CustomCommand[] { myViewCommand };//Dockable edition
        }

        void HandleInvoked(Object sender, EventArgs args)
        {
            if (!myVegas.ActivateDockView("YTPMView"))
            {
                DockableControl dockView = new DockableControl("YTPMView");

                Button mbutton = new Button();
                    mbutton.Size = new Size(120, 40);
                    mbutton.Location = new Point(30, 30);
                    mbutton.Text = "This button";
                    mbutton.Click += new EventHandler(mbutton_Click);
                dockView.Controls.Add(mbutton);

                myVegas.LoadDockView(dockView);
            }
        }

        private void mbutton_Click(object sender, EventArgs e)
        {
            Project activeProject = myVegas.Project;
            try
            {
                activeProject.Tracks[0].Events[0].Start = startl;
            }
            catch(System.Runtime.InteropServices.COMException ex)
            {
                MessageBox.Show(ex.Message);
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.GetType().ToString());
            }
        }

        void HandleMenuPopup(Object sender, EventArgs args)
        {
            myViewCommand.Checked = myVegas.FindDockView("YTPMView");
        }
    }
}

Specifically the problem is when I try this:

activeProject.Tracks[0].Events[0].Start = startl;

It gives back an error that gives the message "Catastrophic failure (Exception from HRESULT: 0x8000FFFF (E_UNEXPECTED))"

This only happens when I try to CHANGE things in the project (even using methods such as 'Copy()'); but when I just load data about the project (e.g., I get the start, length, and end times), it works normally.

What is going wrong? Am I doing something wrong?