My members are getting 404'd all across the forum like when trying to reply to a thread or accessing an option etc.. I'm getting it as well in Admin CP and through the forum when needed to be redirected, I get 404'd..
Can you provide a link?
Also, if you can access it, turn off this setting:
Admin CP -> Configuration -> Server and Optimization Options -> Enable search engine friendly URLs? -> Disabled
See if the above fixes it. If it does, then you have a .htaccess problem.
I'll give that a try, but here's the forum.
http://samsunggalaxys2review.org/forum/
EDIT: One plugin I believe that may have caused this from wordpress is BulletProof Security which modifies the .htaccess. I'll look into it.
Yep I was right, it was the plugin.. Thanks for pointing out the .htaccess otherwise I wouldn't have looked.
Well, after looking at your forum links they are already disabled / turned off.
This could be a cookie problem, although I am not positive. I haven't gotten any 404 errors by browsing your site.