I had the same problem. There seems to be some conflict with disqus andthe function that retrieves the number of comments.
However, you can access the global $post variable. When I checked the value, it showed the correct comment count. So, try using that comment count and bypassing any fetcher functions.
<?php echo $post->comment_count?>
<?php echo ($post->comment_count==1?' comment':' comments');?>
Hope this helps.
