I turned it off, and I also solved my problem. After pulling my hair out for over an hour I resigned myself to a wipe and reinstall. I have never backed up from TM before, but the clone I have was a few weeks ond and I didn't want to lose any data.
I booted into the Recovery Partition and selected my latest Time Machine snapshot, from only a few minutes before I closed Safari and it auto-updated. I thought it would wipe and reinstall, but I was surprised to see it only took about twenty minutes. I guess it does a progressive restore only replacing what has been changed since the snapshot/backup was taken. I didn't know TM restore worked this way.