Can't modify existing Calendar events, not recognized as organizer

[DHarrismac]

With Entourage 2004 I can successfully create events on our corporate exchange server, but
when I open an event I previosly created, I cannot update/cancel it
nor invite new people and so on. It appears that Entourage does not
recognize me as the organizer of the meeting. In fact, I will see
myself invited to my own meeting with my email address (instead of my
Exchange user name).

I am on 10.4.11, Entourage 2004 (fully updated)

Any thoughts would be greatly appreciated!