I wonder if this issue is what broke the drupal planet. Quoting Jamie Holly <hovercrafter@earthlink.net>:
This is more of a heads up. I have had a couple of people contact me that they can't use blogapi on their sites. They are hosted with different companies. Then I had someone using Wordpress tell me the same thing. It turns out there is a bug in libxml2 2.7.1 that is stripping out the opening <.
More info can be found on this Wordpress ticket:
http://trac.wordpress.org/ticket/7771
And it appears that the CVS of libxml 2has been fixed:
http://bugs.php.net/bug.php?id=45996
It appears that as hosting companies are updating then they are breaking xmlrpc (and any other module that might rely on libxml2). I figured I would throw out a warning in case we see an increase in support or tickets on this.
-- Jamie Holly