MySQL create error

gistfile1.aw

$sql = 	"CREATE TABLE {$wpdb->prefix}venuesmeta (
					meta_id bigint(20) unsigned NOT NULL auto_increment,
					venues_id bigint(20) unsigned NOT NULL default '0',
					meta_key varchar(255) default NULL,
					meta_value longtext,
					PRIMARY KEY (meta_id),
					KEY venues_id (venues_id),
					KEY meta_key (meta_key)
					) {$charset_collate};";

[21-Oct-2011 19:56:05] WordPress database error Multiple primary key defined for query ALTER TABLE _venuesmeta ADD PRIMARY KEY (meta_id) made by require, require_once, require_once, require_once, do_action, call_user_func_array, rolla_theme_setup, Rolla_Venues->__construct, Rolla_Venues->rolla_taxonomy_metadata_setup, dbDelta

Is an auto_increment a primary key by default? I'm not sure, just guessing...