"Today a popup asked if I wanted to update to the latest version of Opera. I said no. When I next turned on the computer - it was updated without my permission."
Check Program Files/Opera and confirm whether Opera was actually upgraded. I had a similar experience and discovered it didn't actually upgrade Opera -- I'm still at Presto -- but did completely upend my Opera prefs ini file, totally changing the look and feel of Presto and making it unusable. Until I started digging deep into my system, I also thought I had somehow been upgraded. Solution was to replace the new prefs file with a recent backup copy of the old one.
As I said in the other thread, to try to cram down an upgrade to people who've specifically opted out of upgrades and then destroy the utility of their existing Presto installation by replacing the prefs ini file is more than an ethical lapse.