That's what I thought too. It's not showing up in the protocols list there, for some reason, so I figured it must be something handled internally by Opera.

I did look there, but the problem is in opening a link, not a file type. Specifically a link like "secondlife://Fathom/197/92/1803"

The handler for that URL is set to the wrong program on her computer.

I have a friend who is trying to use your web browser. The program association associated with certain links has become messed up. How does one change program associations in the latest version of Opera?