Running Arduino 1.0.6 on a Mac with OS X 10.8. When I open a sketch by double-clicking on the .ino file, two sketch windows always open. Sometimes it's the one I want and a blank one, sometimes it's two (identical??) copies of the file I want to work on. I get the same behavior if I right-click on the file and Open With/Arduino.
Possibly related, the app seems unable to consistently remember where and what size the window was last time I used it. Often I get two small, square windows that perfectly overlap. Whether one window is properly sized and located or not, the second is always small (the default size?).
I don't recall this behavior from a couple years ago, but that was using an earlier version of Arduino and an earlier version of OSX too.
When I upgraded the app, I just replaced the earlier version with the newer; is there a prefs file somewhere that I could poke or delete?
Other than the problem at launch, the app seems to be working perfectly.