PHP Errors when Previewing Submissions

Not sure where to post this, so please move to wherever necessary.

When I preview a post, the following text is at the top of the Safari browser window (running version from OS X 10.9.2).

[phpBB Debug] PHP Notice: in file /antispam/spam_words.php on line 62: preg_match_all() [function.preg-match-all]: Unknown modifier '±' [phpBB Debug] PHP Notice: in file /antispam/spam_words.php on line 62: preg_match_all() [function.preg-match-all]: Unknown modifier '±' [phpBB Debug] PHP Notice: in file /includes/functions.php on line 4534: Cannot modify header information - headers already sent by (output started at /includes/functions.php:3706) [phpBB Debug] PHP Notice: in file /includes/functions.php on line 4536: Cannot modify header information - headers already sent by (output started at /includes/functions.php:3706) [phpBB Debug] PHP Notice: in file /includes/functions.php on line 4537: Cannot modify header information - headers already sent by (output started at /includes/functions.php:3706) [phpBB Debug] PHP Notice: in file /includes/functions.php on line 4538: Cannot modify header information - headers already sent by (output started at /includes/functions.php:3706)