Ever since I upgraded to WordPress 3 (with BuddyPress 1.2.x), I receive the following fatal error when Gravity Forms tries to display a success message:
Catchable fatal error: Object of class WP_Error could not be converted to string in /---/wp-content/plugins/buddypress/bp-core.php on line 566
This error occurs within a function that is used throughout BuddyPress (bp_core_get_user_domain), and I've only experienced it after submitting a Gravity Forms form.