You may encounter these problems…
1) The SFC-comment feature has a problem with theme packages that use AJAX. For example, the Carrington-blog theme. This function will only work on single post pages. On the main page, where the comments are displayed by clicking on the little word bubble, the function does not appear correctly because the links and images are not preloaded. Turn AJAX off in Appearance>Carrington>Behavior: “Load archives and comments with AJAX”
2) The SFC-comment plug-in hooks into the new comments() function. Themes like Carrington don’t. You’ll need to edit the comment form
The file to edit is /wp-content/themes/carrington-blog/forms/comment.php
You could follow the directions here to add the “Connect with Facebook” button, but DON’T. It will screw up the layout.
Find the line (around 62):
<p class=”comment-form-user-info tight”>
Add all three lines consecutively like this before it:
<?php do_action(‘alt_comment_login’); ?>
3) If you use FireFox as your main browser, you may have a popup blocker installed. This may throw the popup window for Facebook into an infinite loop.