iCal notifications button not working when using rules

Hi There - I set up rules to move iCal event invitations/updates/cancellations to a separate folder that I named "Calendar Invitations" so they don't clog my inbox. With these rules running, new event invitations/updates/cancellations used to show up in the event notifications button that appears on the top left of iCal when you get a new invitation/update/cancellation from someone. I just realized today that the event notifications button hasn't appeared for some time. I went into the "Calendar Invitations" folder I had set up to discover I have invitations/updates/cancellations going back to the end of October that never prompted the event notifications button in iCal to appear.

I turned off the rules and the event notifications button works again. But if I turn the rules back on the event notifications button stops appearing with new invites. Like I said, this used to work just fine with the rules turned on.

The rules simeply say,

if the subject contains "iCal event invitation:"

move message to mailbox "Calendar Invitations"

Any ideas on why iCal no longer recognizes new invitations/updates/cancellations when the rules are turned on?

I am running a mid 2012 MBA with OSX 10.8.2