[javierduce]

There is an issue with fresh installs of bbpress in Buddypress. You shold check if the table wp_bb_posts has been created in your database. Otherwise, you should create it manually:

CREATE TABLE IF NOT EXISTS `wp_bb_posts` (
`post_id` bigint(20) NOT NULL auto_increment,
`forum_id` int(10) NOT NULL default 1,
`topic_id` bigint(20) NOT NULL default 1,
`poster_id` int(10) NOT NULL default 0,
`post_text` text NOT NULL,
`post_time` datetime NOT NULL default ‘0000-00-00 00:00:00’,
`poster_ip` varchar(15) NOT NULL default ”,
`post_status` tinyint(1) NOT NULL default 0,
`post_position` bigint(20) NOT NULL default 0,
PRIMARY KEY (`post_id`),
KEY `topic_time` (`topic_id`, `post_time`),
KEY `poster_time` (`poster_id`, `post_time`),
KEY `post_time` (`post_time`),
FULLTEXT KEY `post_text` (`post_text`)
) ENGINE = MYISAM;

Hope it works.
It did for me.