error when users register

I've removed buddypress from my network, but when users register ther is this error:

Warning: fopen(/home/enigmacs/public_html/wp-content/plugins/remove-buddypress-admin-bar/arit_remove_buddypress_admin_bar.php) [function.fopen]: failed to open stream: No such file or directory in /home/enigmacs/public_html/wp-includes/functions.php on line 3296

Warning: fread(): supplied argument is not a valid stream resource in /home/enigmacs/public_html/wp-includes/functions.php on line 3299

Warning: fclose(): supplied argument is not a valid stream resource in /home/enigmacs/public_html/wp-includes/functions.php on line 3302

any idea? thank you!