Comment 57 for bug 187290

3.) When the inkscape directory contains spaces, such as "C:\Program Files\", you might need to quote script paths (and the code to unquote it looks broken).

Comment #47, https://bugs.launchpad.net/inkscape/+bug/187290/comments/47, has a patch for this, but it needs more testing to see that it works and doesn't break anything else.