[@chrishajer Participant 18 years ago]

WordPress 2.6.* is not compatible with bbPress 0.9.0.2. The alpha bbPress release is cookie-compatible with WordPress 2.6.* and the 1.0 release will be compatible as well.

The solution is to use compatible versions of the software.

https://bbpress.org/forums/topic/wordpress-and-bbpress-integration-101