corrupt Reminders.app

I can't launch Reminders.app on my Mac (10.8.1). Well, the app "launches" but no windows open. And the File menu us empty. Reminders.app on my iPhone works fine.

I believe I must have a corrupt reminder in there that the Mac version is choking on. Reminders works again if I disable Calendars & Reminders in the iCloud System Pane. But as soon as I re-activate it and give Reminders a chance to sync from the cloud it then refuses to open a window.

How can I fix this? It is not an option for me to delete all reminders and re-enter them. There are literally hundreds (thousands?) in there.