Tasky no Worky - "Assembly not found for framework Android...."

Hello. I'm new to Xamarin and am trying to run through the Tasky demo. I can launch any emulator, and I don't get any errors on compile, but the Tasky app is never passed through to the emulator. The only thing I can see wrong is that under References, System, System.Core, and System.XML are red and underneath it says "assembly not found for framework Android (version here)". I've tried 2.3 up to 4.0 and I get the same error every time. Any ideas?

Thanks for reading.