After problems with php-code on every page (is solves - thanks - problem somewhere in the FTP-software...?) I now have upgrade to version 4.0beta1.
Using 'mydefault-emotop' and changed a bit in the CSS. To do this, I had to change the folder 'media' to 777. Joomlacomment works OK!
But, when I changed the folder 'media' back to 755, I get a blank page with error:

Warning: file_exists() [function.file-exists]: open_basedir restriction in effect. File(/mydefault-emotop/index.html) is not within the allowed path(s): (/home/deb7602/:/tmp:/usr/local/lib/php/) in /usr/home/deb7602/domains/http://domainname.nl/public_html/cms/components/com_comment/joscomment/comment.class.php on line 60

!JoomlaComment template not found: mydefault-emotop

It will also work if folder 'media' is set to 775, but I think this is not safe. Is that right?