Well, after using it for some time, the black screen
seems to be "normal".
If it isn't there when you export, it will appear and
you'll have to press AGAIN the export button, just minimize the black screen and continue.
This came out when I got mailed by mr. Gillaume from France.
Also, you can give a try to Inkscape and export from there http://www.inkscape.org/
but i like more sodipodi's interface