WPF MVVM project template

I just downloaded the template and installed it in vs2010 and vs2012.
I then created a new project based on the template .  The files it created have an error.  I am unable to view the mainwindows in design mode.

I've added no code of my own whatsoever.

System.NullReferenceException
Object reference not set to an instance of an object.
   at Microsoft.Expression.DesignHost.Isolation.Remoting.STAMarshaler.WaitForCompletion(NestedCallContext nestedCallContext, BlockingCall call, WaitHandle timeoutSignal)
   at Microsoft.Expression.DesignHost.Isolation.Remoting.STAMarshaler.MarshalOutSynchronous(Action action, Int32 targetApartmentId, WaitHandle aborted, WaitHandle timeoutSignal)
   at Microsoft.Expression.DesignHost.Isolation.Remoting.STAMarshaler.MarshalOut(Action action, Int32 targetApartmentId, WaitHandle aborted, CallSynchronizationMode syncMode, WaitHandle timeoutSignal)

hi,
must say i have no idea what this error is, never encountered it before.
i was not able to reproduce what you are describing, in both VS2010/12, i got no errors and the design view looks fine.

this does not seem to be a problem with my extension.
try googling for it.

I made a new project with this template.  I then created a checkbox and bound it to a bool in the MainWindowViewModel:  
private bool _CanRefreshDate;
        public bool CanRefreshDate
        {
            get { return _CanRefreshDate; }
            set
            {
                if (_CanRefreshDate != value)
                {
                    _CanRefreshDate = value;
                    RaisePropertyChanged(() => CanRefreshDate);
                }
            }
        }

I modified the ICommand for the Refresh button:

public ICommand RefreshDateCommand { get { return new DelegateCommand(OnRefreshDate, CanExecuteRefreshDate); } }

and added the method:

private bool CanExecuteRefreshDate()
        {
            return CanRefreshDate;
        }

Why doesn't this ever disable/enable the Refresh button like I expect it should?  It seems the RaiseCanExecuteChanged() in DelegateCommand.cs never gets fired.

Note:  When I created the project in VS2010, I did:  Online Templates->WPF->WPF MVVM project template.  Not the WPF MVVM Application" this site says.  However, the "More Information" link takes me to this page.

Thanks for the catch. i have fixed this in V4.1
i had no handling for CanExecuteChanged in the DelegateCommand.

I may be missing something really obvious, but when I load this template, there are a bunch of errors even after cleaning? is there something specific I need to do on installation or opening?

what version of VS you have? it works on 2010.
what version of WPF you have? it works on 4.0