Can't dismiss Reminder (custom form)

I was sent a meeting request that shows up in my reminders. When I try to
dismiss it I get the error message:

The custom form cannot be opened. Outlook will use an Outlook form instead.
Cannot locate recurrence information for this appointment.

When I click OK I get the following message:

Cannot turn off the reminder. You may be reminded again. Cannot locate
recurrence information for this appointment.

One more note: The start time always seems to change to the current time
when I open Outlook.

Please help!