Live Writer: Keeps asking for login when posting to wordpress

Hi, I use windows live writer to post to my blog. This worked fine and nothing was changed (upgrade etc). However, now, when I hit the publish butten, the login box for the blog appears (which is fine) and I type in my password as usual. But this login box keeps coming back asking for the password. Over and over agin. Nothing is posted.
Yes, I do know my password and I can login to wordpress.org admin site with this login/password.
What can be the reason for this? Again, worked one day, quit working the other day. No settings were changed.
Thanks!