I have version 6.6.3 on opensuse, and everything was going well with my address to http://localhost:8000/b2evolution/ until I wanted it to use the external address of centauri.servegame.com (which is itself a redirected DNS from noip.com)
Although I can get to things under collection and from the admin.php pages, when I try to click the link on my main web site, it attempts to connect to http://centauri.servegame.com:8000/b2evolution/b2evolution/
I've looked in the database and tried to change the setting for home URLS, and even moved the whole b2evolution to b2old, made a new DB instance and loaded b2evolution again from scratch.
I checked /etc/php5/apache2 and /etc/apache2 and cant find where the system is redirecting even the name localhost to centauri.servegame.com which is somehow embedding the 2nd /b2evolution/
Everything else on the web site works fine with relative addressing, so its something I have done to b2evolution itself.
I have run find and grep looking for servegame.com to try to find what file this might be in, to no avail.