WordPress WordPress Email Notification Plugin

WordPress WordPress Email Notification Plugin v2.3.1 v2.3.1

I have some problem whit install the WordPress Email Notification Plugin v2.3.1. I have following the instructions step by step but i have followings erros! Can any one tells me what i gone to do to get it to work!
I am a new beginner of this so explain it detailed.

Tanks a lot /Apel

In the header following cod is showing…

Warning: mysql_num_rows(): supplied argument is not a valid MySQL result resource in xxx/wp-content/plugins/wp-email-notification/email_notification_2.3.1.php on line 369

Warning: mysql_fetch_assoc(): supplied argument is not a valid MySQL result resource in xxx/wp-content/plugins/wp-email-notification/email_notification_2.3.1.php on line 372

Her is the cod in the email_notification_2.3.1.php

in line 369: $check_existing_nrows = mysql_num_rows($check_existing_result);

in line 372: # Don’t process unless there are entries that need to be e-mailed
while ($future_row = mysql_fetch_assoc($check_existing_result)) {

$send_post_ID = $future_row[‘post_ID’];