Notification Center not listening cross-device.

Why does the notification center not listen when I click on the check-box to state I've completed a task, event, etcetera ? How can I update this, I am totally signed into all extended accounts and using iCloud. When I select that I completed a task, reminder, etcetera, the notification returns and does not go away. I notice that the Notification Center is not stable. It often freezes the computer.

I'm on a new Macbook Pro (Non-Retina) with 8GB memory and all the bells/whistles.

Mountain Lion.