Problem with posting from Windows Live Writer

Windows Live Writer is really quite a nice tool for posting to blogs. But despite of my effort to get it to work with jroller, I've always failed. I have seen someone succeeded posting to jroller, but I always get the following error. Could anyone give me any hint what I'm doing wrong?
Here's what I did to set up jroller in WLW:

1. 
   
2. Start Live Writer and Add a new Weblog Account. Fill in the URL of your weblog, your user name and password at jroller.
   
3. Choose Metaweblog API as the type of weblog. And Type "http://www.jroller.com/xmlrpc" as the Remote posting URL.
   
4. Write a new post, and select Publish. The following error dialog shows up.