adding gravatar to side bar recent comments

Hello!

I’m using the chocolate-lite theme and would like to add to display the gravatars next to the recent comments featured in the side bar. Here is the piece of code associated with the display of recent comments:

[Code moderated as per the Forum Rules. Please use the pastebin]

However if I remove the comments to make that line active, it bugs and I dont see the recent comments anymore and neither do I see avatars.
<?php echo my_avatar($rc_comment->comment_author_email,40,'',$rc_comment->comment_author); ?>

If someone could help.. thanks a lot,

Michael