comments_popup_link

I am using comments_popup_link on my blog in the following way:

<?php comments_popup_link('<img src="t.gif" onmouseout="this.src=\'t.gif\';"
onmouseover="this.src=\'t2.gif\';"/>',
'<img src="t.gif" onmouseout="this.src=\'t.gif\';"
onmouseover="this.src=\'t2.gif\';"/>',
'<img src="t.gif" onmouseout="this.src=\'t.gif\';"
onmouseover="this.src=\'t2.gif\';"/>'); ?>

basically a rollover image.

Now this works fine when placed in the main index.php page.
——
i am updating my blog and have created a comments.php file which now includes the code above.

i am including this comments.php file in the following way from my index.php page:

<div class ="commentsall">
       <?php
         $wp_query->is_single = true;
         comments_template();
         $wp_query->is_single = false;
       ?>
     </div>

When i do this the comment_popup_link is ignored completely!!

Any ideas why??