>> Ok for one thing just pressing the stop button doesn't always work.
You can use the Spacebar to stop the song. (starting and stopping the song with the spacebar is a new feature of 2009.5) Not sure why the stop button isn't always working for you, it works for me. (escape has always worked) Likely you need to press the STOP and hold it a little longer than normal, since the Mac gets busy sometimes (playing Realtracks for example), and maybe it ignores your click. Lemme know if you ever see the same issue with the spacebar.

>> Another thing, is the looping. When i'm in the notation window (unfortunately , they haven't implemented the highlight feature) looping resets back to the beginning.
On the very first row of notation, it will loop to the beginning. That is normal, and is the same for Mac and Windows. Looping everywhere else works correctly, and I just tested that with the latest Mac version. If you can duplicate a problem like that, please let me know, otherwise try it again, from something other than the very first row of notation.

Have Fun!
Peter Gannon
PG Music Inc.