Roundcube / Kontact sync not working

[Lukas Gradl]

Hi!

I successfully set up a Kolab3-Installation on Debian Wheezy.
I can log in, create users, get mails and can add contacts and  
appointments using roundcube.

As a next step I tried connecting using Kontact from a fresh Ubuntu  
13.04 beta (raring) installation (KDE 4.10.1).
I could add a connection to the Kolab-Server by use of the  
Setup-Assistant of Kontact which asked me for the Kolab-Version as well.

I can add appointments and contacts via KDE, thei're displayed  
roundcube as well, I can change them and the changed will get  
displayed in roundcube. But when I add a contact or an appointment in  
roundcube or change one of these, these changes don't reach the  
Kontact-Instance. Even if I change a contact created by Kontact on  
roundcube this change will never reach Kontact, I tried resyncing from  
server via F5 and by rebooting the Ubuntu-Machine but no success.

any tips on this situation?

regards
Lukas