webdav, cannot create file 0x80070780

I have a webdav running on amazon ec2 ubuntu. There, part of the configuration allows myuser access to a folder.

Alias /webdav/myuser /var/www/webdav/myuser
<Location /webdav/myuser>
    DAV On
    AuthType Digest
    AuthName "webdav"
    AuthUserFile /etc/apache2/users.password
    Require user myuser
</Location>

But, trying to access from Windows 7, when I right-click to create a file (inside webdav/myuser) then I get error 0x80070780 as shown in the image.

The same user can create a file in another folder (webdav/public) where access is allowed to valid-user.

What is going on? What can I do?

Problem solved by chown in the server:

sudo chown -R www-data:www-data webdav/myuser