Ok, it just happened to me with Dropbox.

Think I've found a workaround:

You need to rename the executable file not the app.

Here's what I've done:

Rename the app "Opera12"

Right click and 'show package contents' > Contents > MacOS

In there is the executable file - rename that "Opera12"

I did some other stuff with profiles while I was messing around so it may be slightly more complicated than that. Let me know if it doesn't work.

It may break your links or have other consequences, but works fine for me.

I've got both installed with no problems.

My Opera 12 is still in the Applications folder and is renamed OperaOld.app.

You could try starting Safari (if you still have it installed) changing that to the default browser.

Then launch Opera 20 and make that the default browser, having renamed 12.

I would think do a system-wide change which would stop the conflict.

Purely speculation though!

Is this possible?

There is no scenario in which I want a link to open in a new window (unless I specifically choose to do it myself).

Has anyone else had this problem?

I can use a pdf viewer from the Extensions but it does not provide .doc file previews in Dropbox which is what I need.

The plugin does not appear in the Plugin list in Opera. It is installed in the Library as detailed on Opera help pages.

-Opera 20 on Mavericks.

-Latest Adobe Reader installed.

-Opera & Reader reinstalled.

-Computer restarted, etc.

-Tried Chrome, Safari, Firefox – all work without a problem (full PDF & Dropbox preview functionality).

Any suggestions?

I would have thought that Opera could easily port Chrome's PDF reader...