I disabled cached mode and then launched Outlook /cleanreminders.
Thirty-seven old reminders still popped up. I dismissed them. I then renamed
her OST file, enabled cached mode, and launched Outlook. Then a balloon
popped up saying “cannot start the reminder service. Unable to show
reminders.” I googled this and found a forum thread suggesting to use the
/resetfolders switch and that there is a hidden reminders folder in Outlook.


After using the /resetfolders switch the old/duplicate reminders have gone
away and thus far (2 days) have not reoccurred.

"Lanwench [MVP - Exchange]" wrote:

Laura Galusha wrote:
We are using Exchange 2003 SP2.

One of my users is experiencing a problem with duplicate/old reminders
appearing in OWA at home. She will have a list of sometimes as many
as 30 reminders appear when she goes in to OWA - all reminders are old
(weeks/months) and have already been dismissed by her via Outlook
when she is in the office. Sometimes she will also have the
duplicate reminders appear in Outlook (on a day following her OWA
access from home). We have tried using both the /cleanreminders and
/cleansniff switches and neither have corrected this. I have also
applied the hotfix from KB 957208.

The only way I've ever fixed this was with outlook.exe /cleanreminders,
which has always worked. Wild guess...disable cached mode, open Outlook -
is it good? If so, delete or rename her old OST file, open OL and re-enable
it, and reopen it.

I'm setting up my reply to crosspost to microsoft.public.outlook as someone
there may have more advice.