I installed kolab on a virgin gentoo box and couldn’t access web admin. After troubleshooting it appears that /usr/share/php/kolab/admin/ isn’t being copied to /var/www/kolab/htdocs/admin/ . I unmerged and emerged kolab-webadmin-2.1 on my working kolab install and it broke.
2hrs wasted

The solution is to type:
mv /usr/share/php/kolab/admin/templates /var/www/kolab/htdocs/admin/