error message from iCal re iCloud

I continue to get a pop-up error message with the calendar date. "The server responded with an error. The event "coconut spread" was rejected by iCloud because it already exists. There are then the three menu buttons "Ignore", Try again, or revert to server. This is driving me mad. It appears to be rejecting every item on a list in Reminders. i have turned off Reminders in the cloud but this still goes on. I have screen shot of message but can't upload here, apparently