Lanwench [MVP - Exchange]:
I'd exmerge the mailbox to PST and see if the data looks OK therein (viewed
in Outlook) - then I'd delete & recreate the mailbox & exmerge the file back
in.

Ok, I can't use Exmerge because I've only access to client side, with
Outlook or OWA.
I'll ask my administrator to reset my mailbox.

**
In fact this is very strange, have you ever seen a situation like this?

Anyway, I still don't understand WHY I can see the calendar correctly
with "Outlook Today", but NOT from the navigation pane, even if I
/resetfolders and /resetnavpane.

Another point: using an external software (Nokia PC Sync) that access to
my mailbox, I see the "Calendar" folder correctly, and it can manage
correctly the calendar!
**

Lanwench, thank you again!