I was just building a sample app to post on the Xamarin forums for another problem and found I had to turn off both "Fast Assembly deployment" and "Use shared Mono runtime". Without former setting turned off it wouldn't deploy and without the later setting turned off it would crash when it ran. I've been debugging my normal app for a while now with no problems and only ran into this with a newly built app with probably a different Xamarin version.
Any ideas what is going on and how I fix it?