Comment 47 for bug 625140

Daniel,

Unfortunately, the converter doesn't support the Polygon element at all [1], and your file mainly uses it. Thus the exported file if almost empty, the Polygons being replaced by comments.
But there's an easy workaround that consists in converting all parts of your drawing to paths (select all with Ctrl+A, then use Path>Object to Path) before exporting it.

[1] FYI, all the tests and know limitations are available on the Inkscape wiki (http://wiki.inkscape.org/wiki/index.php/SpecFXGExport).