For those that might be interested, we've been able to isolate it down to a Win32 issue and CSDispatcher. Using a straight C# application, we get
Received an exception: System.InvalidOperationException: Cannot read Instance : CSDispatcher.
at System.Diagnostics.CounterDefinitionSample.GetInstanceValue(String instanceName)
at System.Diagnostics.PerformanceCounter.NextSample()
at System.Diagnostics.PerformanceCounter.NextValue()
when trying to read the "Private Bytes" value. I am not sure if it is a bug with the Win32 Perfmon provider or something that CSDispatcher has done to disable that counter.