I also cannot zoom in/out. I have tried clicking in every part of the screen and used the + and - on the top row of the keyboard and also on the numeric keypad.
I have successfully added a new megatree. Not only have I added it, but when I go to the preview it shows up and lights up when I press play. No music yet, but I'm patiently waiting. I'm also able to move models around on the screen and click on save so that part is still working fine. This is with a converted sequence.
I can zoom and use the wheel and ctrl +/- in other programs without a problem.
Running Win 7 Home x64 12gb RAM 1tb hard disk