With the new snapshot 142, I can install Vivaldi with my account in 8.1 and it works fine from the desktop, start menu etc, but the other user on my machine who is a standard user can't execute the vivladi.exe file from desktop, taskbar or start menu,it comes up as "class not registered" and fails to start. 141 worked fine for both accounts.
In which folder are you installing Vivaldi? It must be in a folder that the other user has access to.
I have been installing to the same default location every time and it had been working, but with 142 it stopped working for my other user.
Is this one the default?
If so you'll have to install in another folder where the other user has access, like /Program Files/.
I did that too thinking that was the problem. It will start from the original .exe file but not from a shortcut from that .exe file.. kinda odd.
I read that Chromium Engine has had this problem before, so I am not sure it is so much a problem with V as it is with Chromium itself.