>To the best of my knowledge it does yes. I use Excel via interop. I think I will refactor my logic so that this situation won't hurt, or put a "wait".

A simple wait might be dangerous if you under-estimate the timing. Maybe a semaphore would work (not tested):

   public class Test
    {

        public static ManualResetEvent re = new ManualResetEvent(false);

        public void Doit()
        {
            var bg36 = new BackgroundWorker();
            bg36.DoWork += bg36_DoWork;
            bg36.WorkerReportsProgress = true;
            bg36.ProgressChanged += bg36_ProgressChanged;
            bg36.RunWorkerAsync();

        }

        private void bg36_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
               if ((string)e.UserState== "save ledgers")
	        {
		         SaveLedgers();
                         Test.re.Set();
            }
        }

        public void SaveLedgers()
        {
        }

        private  void bg36_DoWork(Object sender, DoWorkEventArgs e)
        {
            BackgroundWorker bw = (BackgroundWorker)sender;
            bw.ReportProgress(0,"save ledgers");
            Test.re.WaitOne();
            //Continue
        }

    }