Sometime you can't get enough resource to delete all post at one time.
So I fix the code to check 20 post at one time.
open auto-delete-posts.php and find line 398 (gen_query())
if (DEL_PUB_POSTS == $this->settings['DelPostType']) {
$post_status = 'publish';
if ((count($this->settings['DeleteCategory']) == 0) &&
($this->settings['MoveCategory'] == '0') &&
($this->settings['AddCategory'] == '0')) {
echo "No category selected for Delete, Move or Add actions. Unable to preview any posts.";
} else {
$catArray = $this->settings['DeleteCategory'];
$getpost_args = 'numberposts=20&category=';
for ($i = 0; $i < count($catArray); $i++) {
$getpost_args .= $catArray[$i];
if ($i+1 != count($catArray))
$getpost_args .= ',';
}
}
} else {
$post_status = 'draft';
$getpost_args = "numberposts=-1&post_status='$post_status'";
}
$getpost_args .= '&order=ASC&orderby=date';