VS 2008 Rendering Graphics With A BackgroundWorker

I am trying to make a graphics program with mousewheel-controlled zooming using GDI+. My plan is to provide rapid feedback, such as a low resolution render or even just a bounding rectangle, followed by a full resolution render as soon as possible afterwards. It seems logical to me to try a BackgroundWorker for the latter task. This is my first attempt to use one of these, or any other way of multithreading for that matter. Mousewheel events can follow one another much more quickly than I can render to the screen. That means I need to kill any rendering process that is already running and start a new one with the latest value of the zoom scaling factor.[code]The above class coexists with a DrawingSurface class, a UserControl which listens for the ProvideFeedback and ScaledImageReady events and paints the image accordingly. It also raises mouse/keyboard events for the zoom and other tools to deal with. My problem arises in the DO loop waiting for Cancellation to finish. The zooming routine works for one or maybe half a dozen renders, depending on the image size, but then it hangs in that loop and never comes out.