owncloud gnome-shell add online account error 401

1) The release of Ubuntu you are using, via 'lsb_release -rd' or System -> About Ubuntu
Description: Ubuntu 13.04
Release: 13.04
The gnome distribution variant.

2) The version of the package you are using, via 'apt-cache policy pkgname' or by checking in Software Center
gnome-online-accounts:
  Installed: 3.8.2-1ubuntu1
  Candidate: 3.8.2-1ubuntu1
  Version table:
 *** 3.8.2-1ubuntu1 0
        500 http://ppa.launchpad.net/gnome3-team/gnome3/ubuntu/ raring/main amd64 Packages
        100 /var/lib/dpkg/status
     3.6.2-1ubuntu1 0
        500 http://de.archive.ubuntu.com/ubuntu/ raring/universe amd64 Packages

3) What you expected to happen
When I give the details for my http owncloud installation, I would love for goa to succesfully connect and integrate owncloud into my gnome experience.

4) What happened instead:
I get the following red error message above the account form:
"Error connecting to ownCloud server:
Code: 401 - Unexpected response from server"

The owncloud installation (5.0.7) runs on an internet server, address, username and password are correct, I checked several times. A you can see above in 2), I use the gnome3-team ppa.

If there is more information or some tests I might be able to run, give me a hint, please :)

Thanks for all the work in any case!