I just installed WordPress 2.5.1 and the latest release of Windows Live Writer and found that there is an error in xmlrpc.php. This causes the error as shown in the title of this forum.
In
function mw_newPost()
This line, about halfway in the function is incorrect, and its line number will show up in the log of the latest version of Windows Live Writer, when trying to publish a post. In the log the error is further defined as an “undefined function” call.
logIO(’O', ‘Post cats: ‘ . printr($catnames,true));
printr is not a PHP function nor is it defined in the WordPress code.
Instead of “printr”, the correct function name is “print_r”
After making this change the post was published without any other problems:
logIO(’O', ‘Post cats: ‘ . print_r($catnames,true));