Background thread is locking animated gif in windows form

Hello experts,
I have created a windows form in vs 2008, that is multi threaded.  When the heavy work is being performed I would like the form to display an animated gif.  I have added the animated gif to a picure box and i use a backgroundworker control to handle the heavy work.  The animated gif just locks up until the backgroundworker control has finished.  I have no idea why this isnt working.  I have tried building my own background threads using delegate calls and invokes and the same thing happens.  I added the code below is there something else i can do.

Private Sub Quality_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
pb_drawing.imagelocation = "animated.gif"    'I tried doing this and also set the property before the form loads still doesnt work  
  Me.Cursor = Cursors.WaitCursor
            bgworker.RunWorkerAsync()
End Sub


 Private Sub bgworker_DoWork(ByVal sender As Object, ByVal e As System.ComponentModel.DoWorkEventArgs) Handles bgworker.DoWork
  build_drawing_file 'this process takes a while
End Sub

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