Application not responding while BackgroundWorker DoWork

Question

HI,

I am using BackgroundWorker in scanning a document using C#.NET.
The problem is that while I call the BackgroundWorker.RunWorkerAsync() method, application doesn't respond. After finishing the do work it start responding again. As I know BackgroundWorker thread is used to work at background while user can do work in main UI thread... Please make me correct if i am wrong.

Here is the BackgroundWorker code.

            BackgroundWorker backWorker = new BackgroundWorker();
            backWorker.WorkerReportsProgress = true;
            backWorker.DoWork += new DoWorkEventHandler(backWorker_DoWork);
            backWorker.ProgressChanged += new ProgressChangedEventHandler(backWorker_ProgressChanged);
            backWorker.RunWorkerCompleted += new RunWorkerCompletedEventHandler(backWorker_RunWorkerCompleted);
            progressBar.Visible = true;
            backWorker.RunWorkerAsync();
        }

        private void backWorker_DoWork(object sender, DoWorkEventArgs e)
        {
            try
            {
                List<Bitmap> docs = new List<Bitmap>();
                string currFilename;

                // Create a scanner instance (the user can select if more than one)
                ItemClass scanner = (ItemClass)wiaManager.Create(ref missing);

                // Show the standard scanning dialog (this is not a required step...)
                CollectionClass scans = scanner.GetItemsFromUI(
                    WiaFlag.SingleImage, WiaIntent.ImageTypeText)
                    as CollectionClass;

                // If the user clicks Cancel, collection is NULL
                if (scans != null && scans.Count > 0)
                {
                    // Transfer any scanned pictures to disk
                    ItemClass scan;
                    foreach (object wiaObj in scans)
                    {
                        scan = (ItemClass)Marshal.CreateWrapperOfType(wiaObj, typeof(ItemClass));
                       
                        // create temporary file for image
                        currFilename = Path.GetTempFileName();

                        // transfer picture to our temporary file
                        scan.Transfer(currFilename, false);
                       
                        // Create a Bitmap from the loaded file (Image.FromFile locks the file...)
                        using (FileStream fs = new FileStream(currFilename, FileMode.Open, FileAccess.Read))
                        {
                            // KLUDGE: Must wrap the FromStream Image with a new Bitmap.
                            // Otherwise get OutOfMemoryException later when using ColorMatrix on it.
                            docs.Add(new Bitmap(Image.FromStream(fs)));
                            fs.Close();
                        }

                        // Don't leave junk behind!
                        File.Delete(currFilename);

                        if (docs.Count > 0)
                            OpenImage(docs[0]);
                    }
                }
            }
            catch (Exception ex)
            {
                MessageBox.Show(string.Format("Sorry, image did not scan.  Please try again.\n{0}", ex.Message), "Scanner error");
            }
        }

        private void backWorker_ProgressChanged(object sender, ProgressChangedEventArgs e)
        {
            progressBar.Value = e.ProgressPercentage;
        }

        private void backWorker_RunWorkerCompleted(object sender, RunWorkerCompletedEventArgs e)
        {
            progressBar.Visible = false;
            backWorker.ReportProgress(0);
        }

The time where application is not responding to user is while executing the code that I have made bold
// transfer picture to our temporary file
scan.Transfer(currFilename, false);

The output is always ok. I just need to make application respond while scanning document at background.
Please help me if you can.
Thanks in advance.