Startup with specific pages no longer working
I upgraded to 1.7.735.46 (Stable channel) (32-bit), restarted, and my specific page(s) no longer work. I just get a blank window. Resetting that setting does not work either.
I just fixed something for my wife - she was regularly using a website which suddenly stopped displaying certain interactive elements of the page.
I fixed it by deleting all the references to the website in the [user]\AppData\Local\Vivaldi\User Data\Default\Local Storage\ directory. Maybe this would help you too...?
Btw. I made a backup of her "User Data" directory first and made sure I didn't delete things like bookmarks and cookies which also pointed to the site - so I could test which files were causing the problem and restore the profile if anything went wrong.