Whenever I open Unity on my Mac (late 2009 MacBook, OS X 10.6) it opens fine and the different menus show up in the bar but the editor window itself never appears. It was working fine on Lion, but when I downgraded back to 10.6 it started doing this. As far as I know, I haven’t updated 10.6 to whatever it is now. It’s just 10.6.0. Thanks in advance for the help.
I had the same problem (on a MacBook Pro, OS X 10.6.8), but I found a workaround. You said you could still see the menu bar at the top, right? Go to Window > Layout, and choose a layout. Any should work, but I chose Wide. Once I did that, the editor appeared.