Great stuff. I'm on Windows 10 Pro 64. I found the file here: C:\Program Files (x86)\Opera. The previous build being 42.0.2393.517 I may try this later with the version number substitution in the xml file. Will make a copy of the folders just in case.
After trying my patience I downloaded Chrome (!) after swearing it off years ago. It installed and worked beautifully, but I missed mouse gestures terribly. At some point I opened Opera and suddenly it was "looking" correct in every way. Beats me. But I'm going to leave it for now because the problem is solved for the time being.
Thanks so much for ur suggestions.