Still more Ubuntu breakage

Just to follow-up on yesterday's rant, today has a new symptom. I've barely used the computer this past week so I can't imagine what I might have done to cause it.

I was starting to grow suspicious because my office Ubuntu setup had downloaded two updates while my home PC had not. Just now, under my wife's login, I saw the Update Manager prompting her/us to download. When I switched back to my own login, the prompt went away.

Did I do something to indicate I did not want to receive automatic updates? Or, did this version of Ubuntu just spontaneously stop offering them...