[horde] kronolith/CalDAV error

[Ruud Baart]

I use the latest horde installation - all modules up-to-date on a Debian 
wheezy machine (3.12 kernel and phph 5.4.4).

After the last update of Horde webmail 5.2.2 -> 5.2.3 I get with 
Thunderbird 31.2.0/Lightning 3.3.1 the following error in horde logfile 
when I try to create or modify a calender event:
     [kronolith] Call to a member function getInstance() on a non-object 
[pid 5918 on line 296 of "/****/horde/kronolith/lib/Api.php"]

I can't create or modify any calender events with Lightning. The 
calender in Lightning is defined as WebDAV/ICS and worked always 
correctly. As far as I know Thunderbird/Lightning combination is not 
recently changed. I assume Horde Kronolith is the problem.

When I use the web interface or ActiveSync there are no problems.

I have no idea where to look for. Any suggestions?

-- 
Regards,
Ruud Baart