The "ValidateXaml" task failed unexpectedly... beta 1 to beta 2

Anyone else getting this error upon moving from Silverlight 2 beta 1 to beta 2?:

Error 112 The "ValidateXaml" task failed unexpectedly.
System.NullReferenceException: Object reference not set to an instance of an object.
   at MS.MarkupCompiler.ValidationPass.ValidateXaml(String fileName, Assembly[] assemblies, Assembly callingAssembly, TaskLoggingHelper log, Boolean shouldThrow)
   at Microsoft.Silverlight.Build.Tasks.ValidateXaml.XamlValidator.Execute()
   at Microsoft.Silverlight.Build.Tasks.ValidateXaml.XamlValidator.Execute()
   at Microsoft.Silverlight.Build.Tasks.ValidateXaml.Execute()
   at Microsoft.Build.BuildEngine.TaskEngine.ExecuteInstantiatedTask(EngineProxy engineProxy, ItemBucket bucket, TaskExecutionMode howToExecuteTask, ITask task, Boolean& taskResult) 

I've checked the breaking changes list, but without a reference to a particular ...