I had the same problem with my output track after listening to some surround appleloops, I tried your solution and it worked.
But when I dragged and dropped the surround loops I wanted to use into my song, unfortunately the solution didn't work. I even reset the input and output areas. But to no avail.
What I did do was open a previous version of the song and transfered the surround appleloops into it.
The output track appears normal, plenty of insert windows, and all seems to be fine.
I wonder if when you first drop the loops in and an overview is created that this causes the 'problem'..? (if it is a problem).
Your opinion on this would be most appreciated.