Hi Matt, for v2.52 you have to use Cmd instead of Alt, so try Ctrl+Cmd for zoom and Cmd to rotate.

For MoI v3 which has just been released this has been tuned up and the regular Alt should work in v3 as you were expecting. In v3 on the Mac either Alt or Cmd should work the same for the view navigation stuff.

You can get an update to the latest v3 version here: http://moi3d.com/purchase.htm or also the v3 beta is still currently going and will run for the next 2 months before expiring, you can get the v3 beta version here to test with if you want: http://moi3d.com/beta.htm

- Michael