Unity hangs when I try to Debug

I got tired of waiting 15 minutes for all my assets to load, so I created an empty test scene to test my scripts.

Now, with the empty scene when I press the Debug button in MonoDevelop, it launches Unity, but right after the splash screen (when all I can see is the outline of the Unity windows), it hangs (while using 95%+ of my processor).

Everything was working fine (though slowly) with the scene full of models, but the empty scene won't load at all.

However, if I just load the empty scene directly in unity, it loads fine . . . just not from Debug in MonoDevelop.

Any thoughts?

Reduce poly count in level, optimise scripts that your using and delete anything that doesn't need to be there.