[horde] Kronolith Import ics Problem

[Jens Hellermann]

Dear Horde List Members,

I'm busy testing how to import calendars that have been maintained on my 
old system into horde. Some Calendars especially small ones <1 MB  
import without problems. But we have complex calendars that have up to 
20 MB and the import into horde webmail fails. The syslog doesn't give 
out much information:

Jul 29 10:54:24 Horde HORDE: [kronolith] PHP ERROR: Invalid argument 
supplied for foreach() [pid 2126 on line 1619 of 
"/var/www/horde/kronolith/lib/Kronolith.php"]

But his also happens when I import a calendar that will be shown 
correctly after import. The only difference I can see in the log is that 
afterwards login success messages appear in the log often, when 
successfully importing the calendar (I'm on Imap auth):

Jul 29 11:06:54 Horde HORDE: [imp] Login success for 
hellermann at we-do.com (192.168.X.X) to {imap://mail.mydomain.com:993/} 
[pid 2126 on line 157 of "/var/www/horde/imp/lib/Auth.php"]

How can I find out, what is going wrong with the import? Is there a 
logfile I can check, or can I activate loging?

Kind regards, Jens.