I can reproduce it on my devel instance. This bug is a blocker for 1.1.0.

I know where is the issue but out of curiosity, was it even working with 1.0.4? From the 1.0.4 code, it doesn't look like it ever did.

Try this patch:

patch "UI/Scheduler/UIxTimeDateControl.m"

from [631183574d4e5c34310abe33f9bb93af46d40e2f]

to [98577f40ec61370d5a1e157c1c74296a89a57fb4]

#

--- SoObjects/Appointments/SOGoAppointmentObject.m f0cf6fcf283b76e6cc6c91f70735d6b99e6d43be
+++ SoObjects/Appointments/SOGoAppointmentObject.m 87b5ffb64edcb5b7bb4db8c9456d3b0f8f53db1b
@@ -546,6 +546,7 @@
}
else
{

• BOOL hasOrganizer;
  // Event is modified -- sent update status to all attendees
  // and modify their calendars.
  recurrenceId = [newEvent recurrenceId];
  @@ -562,12 +563,12 @@
  oldEvent = (iCalEvent*)[self newOccurenceWithID: recurrenceTime];
  }

• oldMasterEvent

• = (iCalEvent *) [[oldEvent parent] firstChildWithTag: [self componentTag]];

• if ([oldMasterEvent userIsOrganizer: ownerUser])

• oldMasterEvent = (iCalEvent *) [[oldEvent parent] firstChildWithTag: [self componentTag]];

• hasOrganizer = [[[oldMasterEvent organizer] email] length];

• if (!hasOrganizer || [oldMasterEvent userIsOrganizer: ownerUser])
  {
  // The owner is the organizer of the event; handle the modifications

•   [self _handleUpdatedEvent: newEvent fromOldEvent: oldEvent];
  
    // The sequence has possibly been increased -- resave the event.

I applied that patch
and it works nice for me now.
Thanks.

Fixed by http://mtn.inverse.ca/revision/diff/8a33774ff55089b02c43fb1a6d1acfd98521c634/with/ccaab9322e172157de4d07dca19f1e071e7836a4