Hi, I had the same problem.
The problem is that Joomla and OpenGoo use both "id" in their cookie.
The solution is very simple, just define the following setting in ./config/config.php
define('COOKIE_PATH', '/<fill here your topdirectry of OpenGoo>');
sample:
www.mysite.com/opengoodefine('COOKIE_PATH', '/opengoo');
Regards,
frits