Unsolicited calendar invites keep reappearing in Yahoo Calendar

I have calendar invites that randomly pop up in my yahoo calendar . These invites were never sent to me . I did have the email address associated with it in my contacts . Every time I delete them they come right back. The originator of the invite has deleted them from the source. What can I do ?

[Re-Titled by Moderator]

Original Title: Deleted calendar invites