In the 'Write' tab, if you press the 'Preview' button on the 'Post contents' section, it will open a wrong page and report Error 404. In my case, if I write a post in http://planet.gentoo.org/developers/admin.php?blog=64 and I click on the Preview button, a new page opens directing to the following address http://planet.gentoo.org/developers/deathwing00.php
Fixed, though I cant take credit. The solution was making a symlink from 'beandog' to 'beandog.php' in htdocs.