Thanks to Crush over at the Unity forums to post a new version of Mono for the 3.4 release of Unity. Here is the posting with the goods:

http://forum.unity3d.com/threads/97373-Unity-and-Lion-They-play-nice-right?p=681414&viewfull=1#post681414

This fixes the really annoying “lion” bug where your Mono app would crash everytime you tried to resize the window.

I have been working inside of a teeny tiny window for over 2 weeks now since upgrading to Lion!

Nuts!