I have just migrated my blog from FTP publishing to a custom domain on Blogspot. I tend to use Windows Live Writer to write blog posts, but the image publishing didn’t work; If I tried to upload an image through Live Writer I got a “File Upload Failed” with the server returning a 403 error.
Oddly, it worked fine when I posted images directly through Blogger.
Turns out that I needed a Picassa album – Blogger itself could cope with me not having set it up properly, but Live Writer couldn’t. So, just a quick trip to http://picasaweb.google.com, log in with my Google account, answer a few questions and all is now good.