Here at my work we had this happen to an email address no one mails as (because it was a list), but tons of people mailed to. Basically someone who had our address because they mailed us had Klez.E. I'm not sure where the Klez.E list lives, but that's how it works: takes addresses and puts their info in the From: line. You also start receiving infected emails from people on the list. So, if this is the problem, the only "person" who has stolen your identity is either the program or the person/people who wrote it. Problem is, once it gets out there, others get the virus, and unbeknownst to them, they start to email viruses to other people as you. Even worse (in my opinion) is the flood of virus emails you get because your on the list. After getting deluged for a few months, we "solved" the problem by closing the list. Other than cleaning every user's computer, I'm not sure there's a better solution. Hope enough people are now blocked for this virus that that doesn't happen to you.