Re: Need Help! Trunk + RC1 = bad
I know where that constant (which has actually been renamed since) is defined, but I think it’s a much better approach if you install the SVN trunk.
I don’t know of any database/table changes since RC1. If I were you I might consider just copying out your .htaccess and wp-config.php to a safe location (and any theme changes etc you’ve made – you’ll have to reimplement these afterwards). Get the trunk with
svn co https://svn.buddypress.org/trunk and put it into your mu-plugins, and put the .htaccess and wp-config.php files back in place. And crossing my fingers.