Right well.. I am trying to get a forum started now with over 5k posts and I have started a small SEO process. I can't stress that since I've started the SEO process the traffic has gone down I ain't sure why? I got over 2k people on the forum aday now I only barely get over 200 what can I do to improve?
Really the only thing I could tell you is what ever you did to optimize your site did the oppisite so reverse it. Another thing to remember google is pretty slow when it comes to picking up the changes so be patient with the fix.
you need to promote seo forum by email marketing people to notify people about new forum. u need to hire some person who put useful thread and some of them who solve people query so people find its useful and interesting and participate, also u need to build pr of your forum.