Unable to save a calendar item

I run Ubuntu 12.04TLS with
Evolution=3.2.3-0ubuntu6
evolution-mapi=3.2.2-1

The exchange server is a 2007 SP2.
The connection is not secured.

I also saw this message when I tried to save the item:
(evolution:655): libecal-CRITICAL **: e_cal_component_is_instance: assertion `comp != NULL' failed
(evolution:655): libecal-CRITICAL **: e_cal_component_has_rdates: assertion `comp != NULL' failed
(evolution:655): libecal-CRITICAL **: e_cal_component_has_rrules: assertion `comp != NULL' failed
(evolution:655): calendar-gui-WARNING **: send_timezone: Failed to add timezone: Kon tijdzone voor agenda niet toevoegen: Cannot push timezone to cache
(evolution:655): e-attachment-view.c-CRITICAL **: e_attachment_view_get_store: assertion `E_IS_ATTACHMENT_VIEW (view)' failed
(evolution:655): libecal-CRITICAL **: e_cal_client_get_local_attachment_store: assertion `client != NULL' failed
(evolution:655): libecal-CRITICAL **: e_cal_component_get_uid: assertion `comp != NULL' failed
(evolution:655): e-attachment-store.c-CRITICAL **: e_attachment_store_save_async: assertion `E_IS_ATTACHMENT_STORE (store)' failed

I tried to delete the cache but no luck. Any ideas?