@avl
Here's one thing that I noticed right off the bat: I opened up a single browser window with one single tab open and when I go to Windows Task Manager, it shows 14 instances of Opera taking up 488 MB of memory. 14!!!!! And that's only having speed dial open, I haven't even clicked on a website yet. And yes, I verified that Task Manager was showing no lingering instances of Opera before opening this single window/tab.
This just barely started happening after the last update of Opera, so don't send us down a rabbit hole screwing around with troubleshooting and little implications of "This is your problem, what did you do?" The problem is clearly with the last update, so roll it back until you figure out your problem. If that doesn't happen expeditiously, I will abandon this platform. I'm not going to screw around doing 50 hours of your troubleshooting for you and get treated like I'm the problem here.