求救OpenFileDialog打开的困扰，

按钮源代码：
 Private Sub AddHeadPic_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles AddHeadPic.Click
        Dim MyDlg As New OpenFileDialog()
        If (MyDlg.ShowDialog() = DialogResult.OK) Then
            HeadPicture.Image = Image.FromFile(MyDlg.FileName)
            dress = MyDlg.FileName
        End If
    End Sub出现问题：(我是个菜鸟，望高手指教下)未处理 System.AccessViolationException
  Message="尝试读取或写入受保护的内存。这通常指示其他内存已损坏。"
  Source="System.Windows.Forms"
  StackTrace:
       在 System.Windows.Forms.FileDialogNative.IFileDialog.Show(IntPtr parent)    在 System.Windows.Forms.FileDialog.RunDialogVista(IntPtr hWndOwner)    在 System.Windows.Forms.FileDialog.RunDialog(IntPtr hWndOwner)    在 System.Windows.Forms.CommonDialog.ShowDialog(IWin32Window owner)    在 System.Windows.Forms.CommonDialog.ShowDialog()    在 his.updataUser.Button1_Click(Object sender, EventArgs e) 位置 D:\HIS\HIS\updataUser.vb:行号 92    在 System.Windows.Forms.Control.OnClick(EventArgs e)    在 System.Windows.Forms.Button.OnClick(EventArgs e)    在 System.Windows.Forms.Button.OnMouseUp(MouseEventArgs mevent)    在 System.Windows.Forms.Control.WmMouseUp(Message& m, MouseButtons button, Int32 clicks)    在 System.Windows.Forms.Control.WndProc(Message& m)    在 System.Windows.Forms.ButtonBase.WndProc(Message& m)    在 System.Windows.Forms.Button.WndProc(Message& m)    在 System.Windows.Forms.Control.ControlNativeWindow.OnMessage(Message& m)    在 System.Windows.Forms.Control.ControlNativeWindow.WndProc(Message& m)    在 System.Windows.Forms.NativeWindow.DebuggableCallback(IntPtr hWnd, Int32 msg, IntPtr wparam, IntPtr lparam)    在 System.Windows.Forms.UnsafeNativeMethods.DispatchMessageW(MSG& msg)    在 System.Windows.Forms.Application.ComponentManager.System.Windows.Forms.UnsafeNativeMethods.IMsoComponentManager.FPushMessageLoop(Int32 dwComponentID, Int32 reason, Int32 pvLoopData)    在 System.Windows.Forms.Application.ThreadContext.RunMessageLoopInner(Int32 reason, ApplicationContext context)    在 System.Windows.Forms.Application.ThreadContext.RunMessageLoop(Int32 reason, ApplicationContext context)    在 System.Windows.Forms.Application.Run(ApplicationContext context)    在 Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.OnRun()    在 Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.DoApplicationModel()    在 Microsoft.VisualBasic.ApplicationServices.WindowsFormsApplicationBase.Run(String[] commandLine)    在 his.My.MyApplication.Main(String[] Args) 位置 17d14f5c-a337-4978-8281-53493378c1071.vb:行号 81    在 System.AppDomain._nExecuteAssembly(Assembly assembly, String[] args)    在 System.AppDomain.ExecuteAssembly(String assemblyFile, Evidence assemblySecurity, String[] args)    在 Microsoft.VisualStudio.HostingProcess.HostProc.RunUsersAssembly()    在 System.Threading.ThreadHelper.ThreadStart_Context(Object state)    在 System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state)    在 System.Threading.ThreadHelper.ThreadStart()
  InnerException: