Hi again,
Here are some more details about the problem and what workaround I found for myself. My service document didn't require authentication. When authentication was added then some parts of the problem began to disappear. But another problem rose. If the user
didn't save his password (didn't check the "remember my password" checkbox and typed his password every time he was prompted) then when the service required authentication then the wlw sent only the user name (even when a password was typed by the
user). But if the user saved his password then the wlw started to send the password (this seems to be a bug of the wlw). After I added authentication to the service document then the wlw started to pass the user credentials on posting new media (solving my
main problem). After adding authentication the wlw began to download the blog styles properly, too (before that it didn't).
To put a brief summary for all developers that are implementing atompub blogging api for windows live writer:
1. Protect your service document with some type of authentication.
2. Advise the users of your system to save their credentials when prompted by wlw.
Best regards,
Ivan