I have the same problem. First it was one, now overnight, it mulitplied to
three, all reminding me of a common calendar entry, but as SRF indicates
below, the software can't locate the recurrence information.

"SRF" wrote:

How do I delete an orphan reminder in Outlook (2007). The appointment has
been deleted, but the reminder repeats every day and every time any other
reminder is displayed. Trying to dismiss it brings an error message: "Cannot
turn off the reminder. You may be reminded again. Cannot locate recurrence
information for this appointment."