MonoTouch.UIKit.UIViewController could not be resolved to Obj-C

Hi,

Any ideas on how to fix this? I'm getting it on every view controller.

Error updating Xcode project. Could not generate class 'ftrack2ios.DeviceLocation' as its base type 'MonoTouch.UIKit.UIViewController' could not be resolved to Objective-C.

Hint: Try adding [Register ("UIViewController")] to the class definition for MonoTouch.UIKit.UIViewController.

I don't really want to be recreating every view controller - this project has tonnes of them!

Paul