Dear pivic,
The xsltproc included in the latest KiCad package(RC1) does not work as you mentioned. This is RC and, I think, will be fixed shortly.
The workaround for this problem is to use another XSL engine. Please refer the post “BOM generation in “new” Kicad (Windows)”. This is my choice.
If you want to use xsltproc, please refer “Installing an XSLT processor”. There is a nice Web page for this(written in Japanese), but I excluded that because I am new here and can include only two URLs.
Thank you.