I have a very annoying problem with my new IPhone 4S (iOS5) and my IPad 1 (iOS5) on one side and our company's ZIMBRA server on the other side.
All software releases are completely up-to-date. ZIMBRA runs on version 7.1.2.

Since the update to iOS5, not all calendar entries are synched any more. (Yes, I have set "sync all events".) (The sync on my IPad1 running on iOS4 worked like a charm. The problem began exactly after the iOS5 upgrade.)

"Not all" means, that e.g. today I have 5 appointments in my calendar on the ZIMBRA server, all in the same calendar ("calendar"). Currently 4 of these 5 appointments are synced to my IPhone and IPad, one appointment (between the others) is not synched on my IPhone... (Interesting: this event is synched to my IPad currently, but other appointments are missing there, too).

I tried to solve the problem with the following actions:
1. Deleted the configuration several times and set up new on IPhone/IPad.
2. Tried the Exchange protocol and iCal protocol.
3. Disabled E-Mail sync to reduce data traffic.
4. Disabled iCloud completely (except the device localization)

Nothing helped so far.

This means, that I cannot trust the calendars on my IPhone 4S and on my IPad 1 any more.

I posted this question at the Apple support site some time ago, but got no help until now (https://discussions.apple.com/thread...art=0&tstart=0). Now I want to ask you guys here, if somebody had the same problem before...

Any help is highly appreciated!