artifacts on exported png

[rcr]

One of the rendering methods on openstreetmap.org uses inkscape to convert svg files to map tiles and we are noticing some horizontal line artifacts on a small percentage of the resulting png files.
I have tried this with the officail release (Inkscape 0.45.1, built Mar 21 2007) and a recent dev build(Inkscape 0.46dev+devel, built Jan 14 2008).
I'm running on Win XP but others on various linux flavors are also reporting the same problems.

I've uploaded a sample svg is here : http://www.mediafire.com/?22lmdjvejxn
and the sample resulting png here : http://www.mediafire.com/?7gkmowbzybz

Note the horizontal blue lines across the top of the png.
These line are also visible when viewing the svg interactively in inkscape when using some low zoom setting (eg I see a line at zoom 1.6% but not 1.7%)

The command line being used in this instance is :
"C:\Downloads\Inkscape0801141510\inkscape\inkscape.exe" -z -w 256 -h 256 --export-area=0.000000:0.000000:14062.500000:14058.255167 --export-png="C:\tiles_at_home\keep\2096_part-test.png" "C:\tiles_at_home\keep\output-2096-z8.svg"

Contact me if more examples are required.