Hi,

I have solve the probleme too, following last post in this theard.
In my case, it was not enougth

Check your link on
http://www.domaine.com/sitemapindex.xml
if its good.
For me, the problem comme back on
http://www.domain.com/sitemapcategories.xml and other.

I have to change the ligne 2 in every files
sitemapcategories.xml and other

Code:
<?xml-stylesheet type="text/xsl" href="includes/templates/template_default/css/gss.xsl"?>
to

Code:
<?xml-stylesheet type="text/xsl" href="gss.xsl"?>
Regards
olivier