Why wont my variables properly resolve?

here is my plugin activation code

$classified_category_name = 'classified';
$credit_table_name = 'credits';
$credit_table_version = 0.1;

register_activation_hook(__FILE__, 'LBH_Classifieds_Activate');

function LBH_Classifieds_Activate()
{
        global $wpdb;
        global $classified_category_name;
        global $credit_table_name;
        global $credit_table_version;
        $table_name = $wpdb->prefix . $credit_table_name;
        return new WP_Error('broke', __('very broken'));
        if($wpdb->get_var("SHOW TABLES LIKE '$table_name'") != $table_name) {
                $sql = "CREATE TABLE " . $table_name . " (
                        time bigint(11) DEFAULT 0 NOT NULL,
                        amount tinyint(3) DEFAULT 0 NOT NULL,
                        username varchar(50) NOT NULL,
                        UNIQUE KEY username (username)
                );";
                require_once(ABSPATH . 'wp-admin/includes/upgrade.php');
                dbDelta($sql);
        }
        add_option('lbh_db_version', $credit_table_version);
}

but the global variables are empty.

Also, is there any way to print any information from within a plugin? I’ve tried returning a WP_Error, throwing a WP_Error, and all I can ever get is a big yellow box, mostly empty, with “Plugin could not be activated because it triggered a fatal error.”

Thanks,
Joe