HELP cannot delete calendar entries

I need help... probably something i missed stupidly.

When i try to delete an entry in the calendar... the result is... nothing

i click on delete, after javascript validation the right function
delete of class uicalendar runs :

it calls bo->delete_entry($cal_id)
then bo->expunge()

in bo->expunge()

all sems to go right till call to
send_update(MSG_DELETED,$event['participants'],$event);

the call to so->expunge() is never done...

and i get back to the edit page for the event that i wanted to delete.

Details :

in send_update() the execution stops with call to
$GLOBALS['phpgw_info']['user']['preferences'] =
$GLOBALS['phpgw']->preferences->create_email_preferences();

in create_email_preferences() the execution stops with call to
$email_base = CreateObject("email.mail_msg");

i did'nt go further... i guess i missed something whith mail but i
cannot figure what.

phpgw version : ...14.005