Hi Tamsin,
Unfortunately the method you have outlined doesn't seem to work for 2D spirals, on both VW2008 and VW2011. I have no trouble using the duplicate along path function with geometric shapes, straight lines, polylines, whatever, but for some reason not 2D spirals.
Try doing this: Select a 2D locus AND a 2D spiral. Then Edit > Duplicate Along Path.
On my VW2008 copy the dialogue box "no path object is selected" appears.