Crash on start

Hi all - I've just updated a project I've worked on for a while to the latest XF build as well as updated all the project packages. Now when I start the app on the simulator, everything works fine, but when I deploy to a device (iOS both debug and release) it shows the splash screen and crashes. I've tried adding breakpoints in Xamarin Studio in the Main.cs and AppDelegate.cs files, but no break point is ever hit. It seems to crash before anything has loaded. There is also no error message in the Application Output except:

Please ensure your device is connected...
Connected to: K's iPhone
Launching /private/var/mobile/Containers/Bundle/Application/GUID/App.iOS.app -monodevelop-port 10000 -connection-mode usb

I'm lost at how I can debug further? Any thoughts/ideas?

Cheers,
Kolchy