Like you, Chris, I'm getting messages ostensibly from "Apple Security" saying my computer was "locked" and giving me a contact phone number to resolve the issue. At first I was unable to close it down -- first time that has ever happened. Eventually I was able to shut it down, but I suspect there's some kind of bug or virus been planted to disrupt the board. Whether this is connected to the unwelcome ads suddenly appearing I have no idea. I hope Dan can intervene somehow.