The .htaccess does not have the information for caching so clear cache, network deactivate your caching plugin as well as the nivo slider plugin. If present, remove the setting for enabling caching in wp-config too.
Does /wp-admin.php load for that blog at this point?
If not, using phpmyadmin go into wp_blogid_options to see what is being loaded. You can clear those options and see if the blog loads.