The test has been sent to support @ yourdomain I got this, while trying to remove an entity from the entityset:

[InvalidCastException: Unable to cast object of type 'Xtensive.Storage.EntitySet`1[Werp.Model.Models.References.SqlImportTemplate+TpSqlFieldMatch]' to type 'Xtensive.Storage.EntitySet`1[Werp.Model.Models.Base.ImportTemplateBase+TpFieldMatch]'.]
   Xtensive.Storage.Internals.FieldAccessors.CachingFieldAccessor`1.GetValue(Persistent obj) in d:\Home\dataobjects.net\Xtensive.Storage\Xtensive.Storage\Internals\FieldAccessors\CachingFieldAccessor.cs:19
   Xtensive.Storage.Internals.FieldAccessor`1.GetUntypedValue(Persistent obj) in d:\Home\dataobjects.net\Xtensive.Storage\Xtensive.Storage\Internals\FieldAccessor{T}.cs:28
   Xtensive.Storage.Persistent.GetFieldValue(FieldInfo field) in d:\Home\dataobjects.net\Xtensive.Storage\Xtensive.Storage\Persistent.cs:262
   Xtensive.Storage.Internals.ReferentialActions.OnRemoveReference(AssociationInfo association, IEntity owner, IEntity target, SyncContext syncContext, RemovalContext removalContext) in d:\Home\dataobjects.net\Xtensive.Storage\Xtensive.Storage\Internals\ReferentialActions.cs:59
   Xtensive.Storage.ReferentialIntegrity.ClearActionProcessor.Process(RemovalContext context, AssociationInfo association, Entity removingObject, Entity target, Entity referencingObject, Entity referencedObject) in d:\Home\dataobjects.net\Xtensive.Storage\Xtensive.Storage\Internals\ReferentialIntegrity\ClearActionProcessor.cs:23
   Xtensive.Storage.ReferentialIntegrity.RemovalProcessor.ProcessItems(IList`1 entities) in d:\Home\dataobjects.net\Xtensive.Storage\Xtensive.Storage\Internals\ReferentialIntegrity\RemovalProcessor.cs:177
   Xtensive.Storage.ReferentialIntegrity.RemovalProcessor.Remove(IEnumerable`1 entities) in d:\Home\dataobjects.net\Xtensive.Storage\Xtensive.Storage\Internals\ReferentialIntegrity\RemovalProcessor.cs:126
   Xtensive.Storage.Entity.Remove() in d:\Home\dataobjects.net\Xtensive.Storage\Xtensive.Storage\Entity.cs:258
   Werp.Controller.Services.BaseDataObject`1.DeleteItem(Guid id) in D:\Home\Docs\Visual Studio 2010\Projects\Platform\Werp.Controller.Services\BaseDataObject.cs:387
   Werp.Controller.Actions.DeleteButton`1.ActionProcess(ClientResult context) in D:\Home\Docs\Visual Studio 2010\Projects\Platform\Werp.Controller.Actions\DeleteButton.cs:43
   Werp.View.Ext.ActionButtons`1.ButtonClick(Type type, Guid[] selectedIds, Dictionary`2 gridParams, Guid progressId, Object[] constructorParams, Type parameterType, String formData, String parameterWindowId, String parentElementId) in D:\Home\Docs\Visual Studio 2010\Projects\Platform\Werp.View.Ext\ActionButtons.cs:179
   lambda_method(Closure , Object , Object[] ) +560
   FastReflectionLib.MethodInvoker.Invoke(Object instance, Object[] parameters) +91
   FastReflectionLib.MethodInvoker.FastReflectionLib.IMethodInvoker.Invoke(Object instance, Object[] parameters) +70
   Werp.Utils.Helpers.ReflectionHelper.StaticCallMethod(Type type, MethodInfo mi, Object[] args) in d:\Home\Docs\Visual Studio 2010\Projects\Platform\Werp.Utils\Helpers\ReflectionHelper.cs:874
   Werp.View.Ext.ButtonHandler.ExecuteMethod(MethodCallInfo callInfo) in D:\Home\Docs\Visual Studio 2010\Projects\Platform\Werp.View.Ext\Handlers\ButtonHandler.ashx.cs:68
   Werp.View.Ext.ButtonHandler.ProcessRequest(HttpContext context) in D:\Home\Docs\Visual Studio 2010\Projects\Platform\Werp.View.Ext\Handlers\ButtonHandler.ashx.cs:162
   System.Web.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +597
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +266