Upgraded to WP 4.0 and Simple Press 5.5.1.  Now getting database errors, which prevent forum members (including Admin) from viewing posts.  From the PHP error log:

[24-Sep-2014 07:13:51 America/New_York] WordPress database error Unknown column ‘attachments’ in ‘field list’ for query SELECT group_id, wp_sftopics.topic_id, wp_sftopics.forum_id, topic_name, topic_slug, topic_status, topic_pinned, topic_icon, topic_opened, wp_sftopics.post_count, forum_slug, forum_status, forum_disabled, forum_rss_private, wp_sfposts.post_id, post_date, wp_sfposts.user_id, guest_name, guest_email, post_status, post_pinned, post_index, post_edit, poster_ip, source, post_content, NULL AS new_post, blog_post_id, attachments, topic_subs, use_tags, topic_status_set, topic_status_flag FROM wp_sftopics JOIN wp_sfposts ON wp_sftopics.topic_id=wp_sfposts.topic_id JOIN wp_sfforums ON wp_sftopics.forum_id=wp_sfforums.forum_id WHERE wp_sftopics.topic_id=525 ORDER BY post_pinned DESC, wp_sfposts.post_id ASC LIMIT 0, 15 made by require(‘wp-blog-header.php’), require_once(‘wp-includes/template-loader.php’), include(‘/themes/wp-clear321/page.php’), the_content, apply_filters(‘the_content’), call_user_func_array, sp_render_forum, sp_process_template, sp_load_template, include(‘/sp-resources/forum-themes/default/templates/spTopicView.php’), sp_this_topic, spTopicView->__construct, spTopicView->sp_topicview_query, spdbComplex->select, spdb_select

And…

[24-Sep-2014 07:45:05 America/New_York] WordPress database error Unknown column ‘attachments’ in ‘where clause’ for query SELECT topic_id FROM wp_sfposts WHERE wp_sfposts.topic_id IN (1350,1364,1355,1361,1360,1353,1357,1359,1358,1354,1348,1347,1346,1333,1344,1343,1342,1341,1339,1337,1340,1335,1334,1328,1322) AND attachments IS NOT NULL made by require(‘wp-blog-header.php’), require_once(‘wp-includes/template-loader.php’), include(‘/themes/wp-clear321/page.php’), the_content, apply_filters(‘the_content’), call_user_func_array, sp_render_forum, sp_process_template, sp_load_template, include(‘/sp-resources/forum-themes/default/templates/spForumView.php’), sp_this_forum, spForumView->__construct, spForumView->sp_forumview_query, apply_filters(‘sph_forumview_combined_data’), call_user_func_array, sp_plupload_forumview_query, sp_plupload_do_forumview_query, spdb_select

I tried changing themes to 2014, but that didn’t change any behavior.