I posted about this awhile ago. You must have received the www.niyacn.com letter. Clicking on this link sent to you from a friend propogates this letter to all your contacts -- erases your contact list -- and then sets your vacation responder announcement to keep mailing this letter if anyone attempts to contact you! See if your vacation response announcement has been altered. There are a few reports on the 'net about this, but the response from M$ has been tepid.