Thank you!! Going to Google.com and setting the zoom back to 100% took care of it. I had no idea that Opera saved such parameters on a per-website basis. And I also find it somewhat alarming that Opera does actually keep a record somewhere of the websites that I've visited even I empty the cache after leaving each website. Is there a way to delete all those records?
OK, I guess it's not just my settings - which show the plugin installed and enabled, and which point to a DLL that actually exists. So far, it hasn't been a problem, so I'll just wait for Opera 27 to take care of it. Thanks for your replies.
Voilà! Voilà! Mercy buckets! With audio streaming, another slider appears labeled "Opera Internet Browser", and IT is muted. Un-muting that slider did the trick. Whew! Now I don't have to switch to another browser to watch YouTube.
Thanks, you guys.