I changed the directory name of my WP installation a while back, and all hell broke loose. I couldn't log in because the login page was looking for the old location. I couldn't change the directory name because I couldn't log in. The rewrite rules were also going nuts, but I couldn't fix them because I couldn't log in. I tried a synlink--no good. I eventually went into the MySQL database directly and started editing the options--kind of a scary thing to do.
Is there a way to do this kind of a change that will not cause problems? I want to change the directory name again.