Kontact/Akonadi with Kolab3

Hi,

I've installed a Kolab3 server on Debian Wheezy. Everything seems fine 
so far (sending an receiving mails, webmail, etc.). Now I want to 
connect Kontact (4.9 and 4.10 rc1) to this K3 server... Therefore I've 
created an IMAP connection to this server (works!) and a Kolab Akonadi 
Resource. For the Kolab IMAP connection I've chosen "Current Format 
Version: Kolab Format v3".
The calendar is now shown in Kontact, but it doesn't sync, it shows the 
following error message in a grey box at the left cornert:

"An error occured while reading/writing a 
Kolab-Groupware-Object(akonadi id 49 254): no part found".

Any ide how to debug this and what the problem could be?

Cheers,
Tobias

PS: I've read that Akonadi is also used at the server side, but I can't 
find any Akonadi process running. Is this a default part, or an optional 
one?