Comments Not Working On Pages

On all of my pages, I get the following error:

Fatal error: comments_template(): Failed opening required ‘/home/guchuj05/public_html/wp-content/themes/devenir_en_gris’ (include_path=’.:/usr/lib/php:/usr/local/lib/php’) in /home/guchuj05/public_html/wp-includes/comment-functions.php on line 26

For example on this page: http://atennisblog.com/player-websites-atp/

Whether comments are enabled or not. Comments still work on posts.

I haven’t touched either the comment file in the theme or in wp-includes/comment-functions.php & the comments were working before, so I don’t know what happened.

Can anyone help??
Thanks!!!