I posted before from the WordPress iPhone application when it was released. Its pretty nifty. When they upgraded it to 1.1 though I could no longer get it to work on my blog anymore. I was mighty confused since it worked for every other blog that is hosted on my server, but not mine.
I finally did some digging into the problem and for some reason my blog wasn’t outputting an RSD link which is needed for the application to find the XML-RPC endpoint. A quick grep -R rsd found the issue.
remove_action('wp_head', 'rsd_link');
That was hiding out in my functions.php file. I removed it and I’m cooking along with the iPhone WordPress application again. Beware if your theme does something similar. Found and fixed just before leaving town!
Thank you for this information. :)