All of sudden the forum just stopped working today.  It's been working fine for a week or so, but now when I try to login (as a different user other than admin) or post a reply or a topic, it just sends me back to my home page.  I can SEE the forum, I just can't do anything with it.  I thought maybe it was a permalink issue, so I went to Toolbox and clicked on update and it says “ahah error: 404 Not Found”.  What's going on?  I checked under pages and it's still listed, I can view it, so why isn't it found?

I had some bandwidth issues today and so I turned on WP Supercache, which is the only thing I can think of that messed things up because I haven't made any other changes lately.  But I added /forum/ to the lists of pages not to cache and when that didn't work, I cleared the cache and completely turned off the plugin and I'm still having these problems.  I tried clearing my browser cache and even using it in another browser and I'm still not able to do anything. 

I'm using the newest version of the plugin and WP 2.6. 

You can see it here: http://suzannemcminn.com/forum/

Any ideas what's going on?

The error log is pointing to mysql problems.  It's basically saying the table doesn't exist even though it does (I can still VIEW the forum and admin area).  I've already contacted my host.  But if anyone has any ideas about why this would happen that would be helpful.  Was turning supercache the problem or is this completely unrelated?

I followed the supercache plugin author's instructions for complete removal, so it's gone now, but I'm still have the same problem with the forum.  I checked my .htaccess and I updated my permalinks.  But I can't update the forum permalink, because when I do, it says:  Current Permalink: ahah error: 404 Not Found.  In fact in the admin area at the top of the forum options it also says that (even though I can see all the options, I just can't update anything without getting a 404 error).

I checked the timestamp of the mysql errors and they seem to be from the morning, so they may not be related.  Although it's possible the forum stopped working this morning and I didn't notice until this afternoon.  I didn't turn on supercache until this afternoon, though, so if these errors were generated this morning, then it looks like turning on supercache didn't affect anything.

Here are the errors though:

[26-Aug-2008 10:55:15] WordPress database error MySQL server has gone away for query SELECT topic_subs FROM sm_sftopics WHERE topic_id=17 made by sf_email_notifications
[26-Aug-2008 10:55:16] WordPress database error MySQL server has gone away for query SELECT COUNT(topic_id) FROM sm_sftopics WHERE forum_id=1 made by sf_build_forum_index
[26-Aug-2008 10:55:16] WordPress database error MySQL server has gone away for query SELECT post_id FROM sm_sfposts WHERE forum_id = 1 ORDER BY post_id DESC LIMIT 1 made by sf_build_forum_index
[26-Aug-2008 10:55:16] WordPress database error MySQL server has gone away for query UPDATE sm_sfforums SET post_id=NULL, topic_count=0 WHERE forum_id=1 made by sf_build_forum_index
[26-Aug-2008 10:55:16] WordPress database error MySQL server has gone away for query SELECT topic_sort
             FROM sm_sftopics
             WHERE topic_slug='whats-cookin-today' made by sf_get_topic_sort
[26-Aug-2008 10:55:16] WordPress database error MySQL server has gone away for query SELECT post_id, post_index FROM sm_sfposts WHERE topic_id = 17 ORDER BY post_pinned DESC, post_id ASC made by sf_build_post_index
[26-Aug-2008 10:55:16] WordPress database error MySQL server has gone away for query UPDATE sm_sftopics SET post_id=NULL, post_count=-1 WHERE topic_id=17 made by sf_build_post_index
[26-Aug-2008 10:55:16] WordPress database error MySQL server has gone away for query SELECT message FROM sm_sfnotice WHERE id='74.193.176.35' AND item='sfmessage' made by get_sfnotice
[26-Aug-2008 10:55:16] WordPress database error MySQL server has gone away for query INSERT INTO sm_sfnotice (id, item, message, ndate) VALUES ('74.193.176.35', 'sfmessage', '0@New Post Saved  - Notified: Administrator', now()) made by update_sfnotice
[26-Aug-2008 10:55:16] WordPress database error MySQL server has gone away for query SELECT topic_sort
             FROM sm_sftopics
             WHERE topic_slug='whats-cookin-today' made by sf_get_topic_sort
[26-Aug-2008 10:55:16] WordPress database error MySQL server has gone away for query SELECT topic_id
             FROM sm_sftopics
             WHERE topic_slug='whats-cookin-today' made by sf_get_topic_id
[26-Aug-2008 10:55:16] WordPress database error MySQL server has gone away for query SELECT post_id FROM sm_sfposts WHERE topic_id =  ORDER BY post_pinned DESC, post_id ASC made by sf_determine_page
[26-Aug-2008 10:55:16] PHP Warning:  Cannot modify header information - headers already sent by (output started at /home/suzannem/public_html/wp-includes/wp-db.php:517) in /home/suzannem/public_html/wp-includes/pluggable.php on line 770

Permissions!  That was it!  I had changed the wp-content folder to 777 this afternoon.  When I switched back to 755 the forum started working again. 

That's really strange.  I've had problems where things didn't work because it WASN'T set to 777 but never because it WAS.

Anyway, thanks!

glad its fixed, but very odd error for permissions like that…  usually get internal 500 errors not mysql errors..  but its working - all that really matters…