I (along with other members here from what I remember) had issues upgrading/re-importing 2dToolkit where Unity would crash during the "compiling scripts" step. I think some people established that it was a general Unity bug with OSX. Just verifying that upgrading to the newest version of Unity (4.1.3) resolves the crashing bug, and I've yet to have it fail on me when importing any 2dToolkit packages.