[kronolith] Fwd: lightning vs kronolith

[marco perugini]

hi all! this is my scenario:

client os - linux mint 16
server os - scientific linux 6.5
tb - thunderbird 24.6.0
cal - lightning 2.6.6
webm - horde groupware webmail edition 5.2.2
webc - kronolith 4.2.2
dav - horde_dav 1.1.0
httpd - httpd-2.2.15-31.sl6.x86_64

I'm focusing on remotely managing horde calendars from TB/lightning via 
calDAV, I followed the instructions provided @ 
http://wiki.horde.org/KronolithSunbird

when I create and share a calendar from my own account I can add it in 
lightning without any problem [I can add/modify/delete events, dismiss 
reminders, ...]. success log is linked from 
https://www.dropbox.com/s/z0ifgukxfkraxhb/good_boot_my_cal.log?dl=0

the problem is when I try to add another user's shared calendar, I get 
the error linked from 
https://www.dropbox.com/s/nub31sxthiriqna/TB%20lightning%20rem%20cal%20error.png?dl=0 
and I can't do anything while horde.log give me "EMERG: HORDE 
[kronolith] Call to a member function toHash() on a non-object [pid 4825 
on line 686 of "/var/www/html/webmail/kronolith/lib/Application.php"]"

I've double checked every available permission on this calendar for my 
account; I provided for the web server log 
[https://www.dropbox.com/s/y01nawg1f816k3o/ssl_access.log?dl=0] and 
thunderbird console output 
[https://www.dropbox.com/s/ry8zcnfcomxwq6y/bad_boot_other_cal.log?dl=0]

in the last month the issue drove me crazy, I'm not even sure this is 
all about horde/kronolith bug, maybe ticket #12380? btw it doesn't seem 
to be thunderbird issue, I'm really running out of ideas here...

can someone help me?
thanks+regards