iPhone WordPress XML-RPC issue fix
Many iPhone users have not been able to add their blog to the iPhone due to the client not being able to find the xmlrpc.php file. Because there is no way to manually set the location of the file, if the client cannot find it, it errors out, telling you to contact WordPress support. Well, I cannot wait for WordPress support, and found an easy temporary fix (until a new version of the client is released). The problem is with the theme.
In every theme, this line should be just before the tag: < ? wp_head(); ?>. If this line is there, but you still get the xml-rpc error, then the client is having trouble seeing it (well, the rendered version, which has the location of your xmlrpc.php). Easy solution? Change your theme.
The client only needs to see the location when you add the blog, but never checks it again. Change your theme to the default WordPress theme. Then add your blog to your iPhone WordPress client. Then change your theme back. It works!