System.Runtime.RemotingException in simple XAML file

System.Runtime.RemotingException in simple XAML file

I have a WPF application which is giving me a very very annoying error
System.Runtime.Remoting.RemotingException [12068] Designer process
terminated unexpectedly!
The number between [] changes each time
The XAML is very simple
<UserControl x:Class="STC.Reports.ReportGenerator.Views.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml">
</UserControl>
This has wasted me hours and hours
Does anyone know anything that could help?
I cant get any more information than that above
Even though I have told VS to break on these Exceptions it doesnt
I have also tried to attach another VS and that makes no difference
I have repaired my installation of VS (2012 Professional)
I have also updated to Update 3
This is even happening when I create a brand new WPF application
Everything seems fine initially, then VS just hangs and the remoting error
occurs
Paul