Unity 4.1 hangs/freezes on startup (Mac)

I downloaded Unity 4.1 yesterday, installed the free license to my Applications folder, and the Unity froze as soon as I double clicked on it to open it. I can CMD+Tab over to it, it shows that it's open, but when I've tabbed over to it there's no response, and its menus and name don't show in the menu bar at the top of the screen.

It's frozen. I have to force quit. If I open it again, it complains about a temp file being locked, but I found the temp folder and deleted it, so it no longer has that problem, it only FREEZES now, big help.

I've done what this thread says http://answers.unity3d.com/questions/10086/Unity-Crashes-on-startup.html and done sudo su from the terminal. Same problem; it freezes/hangs on startup.

I'm on an iMac, i5 2.66Ghz, 4 GB RAM, OSX 10.6. Help me please?

I'm so keen to get going on some game creation. :( <- sad face.