I have noticed in Alerts and Activities (I saw this yesterday also) numerous alerts some active for more than 200 days.
I have tried to clear them and it seems to hang the application. Then going back in, I see no alrts.
I set up alerting to send me an e-mail and I am getting an e-mail for the same alert every ten minutes now, but I am unable to clear any of them.
As of now, when I go into clear them, nothing is showing, when I saw them before.