[Plugin: PHPBB Single Sign On] Fatal error: Cannot redeclare validate_username()

I am using HPBB Single Sign On, with WordPress 3.1 and phpBB 3.0.8

It work great with the admin account, but any other account and new accounts, simply cannot login.

Here is the error when i try logging into wordpress.

Fatal error: Cannot redeclare validate_username() (previously declared in /………./public_html/dasocial/wp-includes/user.php:1328) in /………./public_html/dasocial/forums/includes/functions_user.php on line 1610

OTHER INFO:
Reccomended Current OK ?
Files
auth_wpbb.php 0.7.1 0.7.1 OK
common.php 0.7.1 0.7.1 OK
common-orig.php – Original OK
Configurations
Auth Mode wpbb wpbb OK
Wordpress Path Variable /forums/ OK

Also, if i disable the plugin, i can login separately on both installations.