I've just installed a fresh copy of SMF 2.0 RC3 along with the latest version of SA Facebook Connect, and having a problem with Admin \ Features and Options.
When I save anything, even if I don't make any changes, on this Admin page, I get a 400 error. Now I was able to find out what the error was, but I'm on a different computer now and it's not showing for some reason. It was something to do with a Facebook Connect .js file on a Facebook URL.
No other Admin pages have this problem. Any ideas? I'll try and get the full error and post.