I set up a company-wide shared calendar as the user Admin. I'm experiencing two problems.

1) I "remove" users that are no longer with the company, but when I come back as admin, they still show up

2) This one is more pressing, and I know I saw a solution somewhere once, I just can't find it. Many users didn't pay attention the email notice about the shared calendar, and deleted it rather than "accepting" it. Now I can't share it with them again.

Can anyone help me out with either (or both) of these ?