I have Opera set as my default web browser. (This is on a Windows 7 system.) Thus, when I click on a link in some external program, such as Thunderbird or Acrobat, the page loads in a new tab in my Opera window.
For some reason, the new tab that opens is always a private tab -- which means that it doesn't show up in my history or my closed-tabs list when I close it.
Why is this happening? Or, more to the point, how can I change my settings to make it not happen?