Problem with creation of blog on my multisite

Please I need help on the creation of a site on my multisite but when i try to register the site this is what I get below

Warning: array_keys() [function.array-keys]: The first argument should be an array in /home/..../wp-content/plugins/bbpress/includes/core/capabilities.php on line 453

Warning: Invalid argument supplied for foreach() in /home/..../wp-content/plugins/bbpress/includes/core/capabilities.php on line 453

Warning: Cannot modify header information - headers already sent by (output started at /home/..../wp-content/plugins/bbpress/includes/core/capabilities.php:453) in /home/..../wp-includes/pluggable.php on line 881

I tried registering the sub-domain site "help" on What have I done wrong?