Webcal: cannot save calendar due to multiple assignement to same column "write_date"

[Eric Caudal - www.elico-corp.com]

I try to setup a calendar in thunderbird (3.19) in webcal using the following address
https://monserver.net:8071/webdav/training2/calendars/users/admin/c/Meetings
I can read the calendar in TB but when I have alarms and want to snooze or create a new appointment, there is an error saying I cant write to it with the following error in openerp log:

[2011-04-21 20:38:48,732][training2] DEBUG:https:MultiHttpHandler init for ('', 57763)
[2011-04-21 20:38:59,365][?] DEBUG:https:Secure ('AES256-SHA', 'TLSv1/SSLv3', 256) connection from ('', 61051)
[2011-04-21 20:38:59,858][?] INFO:auth:Found user="admin", passwd="***" for db="training2"
[2011-04-21 20:39:00,318][training2] ERROR:db.cursor:Programming error: multiple assignments to same column "write_date"
, in query update crm_meeting set "edit_all"=%s,"description"=%s,"date_deadline"=%s,"date"=%s,"duration"=%s,"location"=%s,"recurrent_id"=%s,"class"=%s,"state"=%s,"base_calendar_url"=%s,"exdate"=%s,"write_date"=%s,"exrule"=%s,"base_calendar_alarm_id"=%s,"organizer"=%s,"name"=%s,write_uid=%s,write_date=now() where id IN %s
[2011-04-21 20:39:00,318][training2] WARNING:webdav:Cannot save 28.ics: multiple assignments to same column "write_date"

[2011-04-21 20:39:00,319][training2] WARNING:webdav:Cannot PUT to https://monserver.net:8071/training2/calendars/users/admin/c/Meetings/28.ics: Operation failed
[2011-04-21 20:39:00,319][training2] DEBUG:DAV.WebDAVServer:Use send_body method
[2011-04-21 20:39:00,320][training2] DEBUG:https:MultiHttpHandler init for ('', 61051)