Error initializing xamarin extensions in VS2012

I have a solution which contains an android project, and iOS project, and some other non-xamarin projects. When I try to open the solution, I receive the following errors: "There was an error attempting to initialize the Mono for Android extension" and "Xamarin.iOS encountered the following error(s): Xamarin.iOS initialization failed."

Below is the detailed error message for the android plug-in; the error message for the iOS plugin is nearly identical, so I haven't included it here.

System.ComponentModel.Composition.CompositionException: The composition produced multiple composition errors, with 3 root causes. The root causes are provided below. Review the CompositionException.Errors property for more detailed information.

1) No exports were found that match the constraint: 
    ContractName    Mono.VisualStudio.Extension.Commands.ICommandManager
    RequiredTypeIdentity    Mono.VisualStudio.Extension.Commands.ICommandManager

Resulting in: Cannot set import 'Mono.Android.VisualStudio.MonoAndroidPackage.Commands (ContractName="Mono.VisualStudio.Extension.Commands.ICommandManager")' on part 'Mono.Android.VisualStudio.MonoAndroidPackage'.
Element: Mono.Android.VisualStudio.MonoAndroidPackage.Commands (ContractName="Mono.VisualStudio.Extension.Commands.ICommandManager") -->  Mono.Android.VisualStudio.MonoAndroidPackage

2) No exports were found that match the constraint: 
    ContractName    Mono.VisualStudio.Extension.Events.IShellEvents
    RequiredTypeIdentity    Mono.VisualStudio.Extension.Events.IShellEvents

Resulting in: Cannot set import 'Mono.VisualStudio.Extension.TastyPackage.ShellEvents (ContractName="Mono.VisualStudio.Extension.Events.IShellEvents")' on part 'Mono.Android.VisualStudio.MonoAndroidPackage'.
Element: Mono.VisualStudio.Extension.TastyPackage.ShellEvents (ContractName="Mono.VisualStudio.Extension.Events.IShellEvents") -->  Mono.Android.VisualStudio.MonoAndroidPackage

3) No exports were found that match the constraint: 
    ContractName    Mono.VisualStudio.Extension.Diagnostics.IUserMessageService
    RequiredTypeIdentity    Mono.VisualStudio.Extension.Diagnostics.IUserMessageService

Resulting in: Cannot set import 'Mono.VisualStudio.Extension.TastyPackage.UserMessages (ContractName="Mono.VisualStudio.Extension.Diagnostics.IUserMessageService")' on part 'Mono.Android.VisualStudio.MonoAndroidPackage'.
Element: Mono.VisualStudio.Extension.TastyPackage.UserMessages (ContractName="Mono.VisualStudio.Extension.Diagnostics.IUserMessageService") -->  Mono.Android.VisualStudio.MonoAndroidPackage
   at System.ComponentModel.Composition.CompositionResult.ThrowOnErrors(AtomicComposition atomicComposition)
   at System.ComponentModel.Composition.Hosting.ImportEngine.SatisfyImportsOnce(ComposablePart part)
   at System.ComponentModel.Composition.Hosting.CompositionContainer.SatisfyImportsOnce(ComposablePart part)
   at System.ComponentModel.Composition.AttributedModelServices.SatisfyImportsOnce(ICompositionService compositionService, Object attributedPart)
   at Mono.VisualStudio.Extension.TastyPackage.Initialize()
   at Mono.Android.VisualStudio.MonoAndroidPackage.Initialize()