Did you happen to click on a Tripod photos link and enter your Yahoo login info? I had this happen to me recently. I don't know why my scatterbrain entered in Yahoo info into a Tripod site, but that was how the thief took my login and changed it. I suggest seeing the post below this called Yahoo Customer Service phone number. I posted the email to contact security directly. If they cannot help me, I will go with a hacker to get it back. I just want that account back because of age and everyone knows me on some names that I use on it.