Cannot read one instance of this recurring appointment

Hi,=20

I have a problem on some Outlook 2003 (linked to an=20
Exchange 2003 server).=20
I created an appointment that repeats itself each week.=20
I double click the appointment, choose "this occurrence"=20
and do some changes into it, I want to save it and I get=20
the following message:=20

"Cannot read one instance of this recurring appointment.=20
Close any open appointments and try again, or recreate=20
the appointment."

Office 2003 is a clean install, not an upgrade. I deleted=20
and recreated the appointment, installed the latest SP=20
and patches, deleted the frmcache.dat, but the problem is=20
still there.

The issue appears ONLY on the locally installed Outlook=20
(some laptops). When activate the =AB Cached Exchange=20
Mode =BB function the problem disappears. If deactivated,=20
the problem persists.=20

The local users use Citrix servers to access Outlook, and=20
they don't have any problem. The =AB Cached Exchange Mode =BB=20
option is grey on the Citrix server. It is not available.

Any ideas on how to fix the problem without being forced=20
to activate the =AB Cached Exchange Mode =BB option on the=20
laptops?

Thank you.