IIS7 + NHibernate: Illegal operation attempted on a registry key that has been marked for deletion

We have an asp.net MVC app using Fluent Nhibernate running on top of IIS7 & Windows Sever 2008. Frequently (although so far we have yet to consistently reproduce it) after a build we get a yellow screen of death with this exception:

[COMException (0x800703fa): Illegal operation attempted on a registry key that has been marked for deletion. (Exception from HRESULT: 0x800703FA)]
   System.Reflection.Assembly._nDefineDynamicModule(Assembly containingAssembly, Boolean emitSymbolInfo, String filename, StackCrawlMark& stackMark) +0
   System.Reflection.Emit.AssemblyBuilder.DefineDynamicModuleInternalNoLock(String name, Boolean emitSymbolInfo, StackCrawlMark& stackMark) +381
   System.Reflection.Emit.AssemblyBuilder.DefineDynamicModuleInternal(String name, Boolean emitSymbolInfo, StackCrawlMark& stackMark) +105
   System.Reflection.Emit.AssemblyBuilder.DefineDynamicModule(String name, Boolean emitSymbolInfo) +83
   Castle.DynamicProxy.ModuleScope.CreateModule(Boolean signStrongName) +206
   Castle.DynamicProxy.ModuleScope.ObtainDynamicModuleWithWeakName() +63
   Castle.DynamicProxy.Generators.Emitters.ClassEmitter.CreateTypeBuilder(ModuleScope modulescope, String name, Type baseType, Type[] interfaces, TypeAttributes flags, Boolean forceUnsigned) +78
   Castle.DynamicProxy.Generators.Emitters.ClassEmitter..ctor(ModuleScope modulescope, String name, Type baseType, Type[] interfaces, TypeAttributes flags, Boolean forceUnsigned) +69
   Castle.DynamicProxy.Generators.Emitters.ClassEmitter..ctor(ModuleScope modulescope, String name, Type baseType, Type[] interfaces) +36
   Castle.DynamicProxy.Generators.BaseProxyGenerator.BuildClassEmitter(String typeName, Type parentType, Type[] interfaces) +140
   Castle.DynamicProxy.Generators.ClassProxyGenerator.GenerateCode(Type[] interfaces, ProxyGenerationOptions options) +648
   Castle.DynamicProxy.ProxyGenerator.CreateClassProxy(Type classToProxy, Type[] additionalInterfacesToProxy, ProxyGenerationOptions options, Object[] constructorArguments, IInterceptor[] interceptors) +139
   Castle.DynamicProxy.ProxyGenerator.CreateClassProxy(Type classToProxy, Type[] additionalInterfacesToProxy, IInterceptor[] interceptors) +39
   NHibernate.ByteCode.Castle.ProxyFactory.GetProxy(Object id, ISessionImplementor session) +416

[HibernateException: Creating a proxy instance failed]
   NHibernate.ByteCode.Castle.ProxyFactory.GetProxy(Object id, ISessionImplementor session) +642
   NHibernate.Tuple.Entity.AbstractEntityTuplizer.CreateProxy(Object id, ISessionImplementor session) +49
   NHibernate.Persister.Entity.AbstractEntityPersister.CreateProxy(Object id, ISessionImplementor session) +102
   NHibernate.Event.Default.DefaultLoadEventListener.CreateProxyIfNecessary(LoadEvent event, IEntityPersister persister, EntityKey keyToLoad, LoadType options, IPersistenceContext persistenceContext) +255
   NHibernate.Event.Default.DefaultLoadEventListener.ProxyOrLoad(LoadEvent event, IEntityPersister persister, EntityKey keyToLoad, LoadType options) +400
   NHibernate.Event.Default.DefaultLoadEventListener.OnLoad(LoadEvent event, LoadType loadType) +923
   NHibernate.Impl.SessionImpl.FireLoad(LoadEvent event, LoadType loadType) +169
   NHibernate.Impl.SessionImpl.InternalLoad(String entityName, Object id, Boolean eager, Boolean isNullable) +310
   NHibernate.Type.EntityType.ResolveIdentifier(Object id, ISessionImplementor session) +211
   NHibernate.Engine.TwoPhaseLoad.InitializeEntity(Object entity, Boolean readOnly, ISessionImplementor session, PreLoadEvent preLoadEvent, PostLoadEvent postLoadEvent) +527
   NHibernate.Loader.Loader.InitializeEntitiesAndCollections(IList hydratedObjects, Object resultSetId, ISessionImplementor session, Boolean readOnly) +544
   NHibernate.Loader.Loader.DoQuery(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies) +1158
   NHibernate.Loader.Loader.DoQueryAndInitializeNonLazyCollections(ISessionImplementor session, QueryParameters queryParameters, Boolean returnProxies) +105
   NHibernate.Loader.Loader.LoadEntity(ISessionImplementor session, Object id, IType identifierType, Object optionalObject, String optionalEntityName, Object optionalIdentifier, IEntityPersister persister) +472
   NHibernate.Loader.Entity.AbstractEntityLoader.Load(ISessionImplementor session, Object id, Object optionalObject, Object optionalId) +77
   NHibernate.Loader.Entity.AbstractEntityLoader.Load(Object id, Object optionalObject, ISessionImplementor session) +30
   NHibernate.Persister.Entity.AbstractEntityPersister.Load(Object id, Object optionalObject, LockMode lockMode, ISessionImplementor session) +182
   NHibernate.Event.Default.DefaultLoadEventListener.LoadFromDatasource(LoadEvent event, IEntityPersister persister, EntityKey keyToLoad, LoadType options) +174
   NHibernate.Event.Default.DefaultLoadEventListener.Load(LoadEvent event, IEntityPersister persister, EntityKey keyToLoad, LoadType options) +194
   NHibernate.Event.Default.DefaultLoadEventListener.OnLoad(LoadEvent event, LoadType loadType) +923
   NHibernate.Impl.SessionImpl.FireLoad(LoadEvent event, LoadType loadType) +169
   NHibernate.Impl.SessionImpl.Get(String entityName, Object id) +191
   NHibernate.Impl.SessionImpl.Get(Type entityClass, Object id) +139
   NHibernate.Impl.SessionImpl.Get(Object id) +136
   Huddle.DataAccess.Persistence.Repository`1.FindById(Int32 id) +281
   Huddle.WebSite.Global.GetWorkspace() +241
   Huddle.WebSite.Global.Application_BeginRequest(Object sender, EventArgs e) +437
   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +80
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +171

It seems a few other people have found the same problem although no one seems to have a solution, any ideas?

This sounds like something I've seen with COM+ and MSMQ on Windows 2008. What happens is that Windows 2008 unloads the user registry hive as soon as the user is logged off, regardless of any remaining open handles. You should see entries in the event log that the hive was unloaded with processes still using it.

There is a GPO that can be set to prevent this from happening (DisableForceUnload)

More information here:

http://blogs.msdn.com/distributedservices/archive/2009/11/06/a-com-server-application-may-stop-working-on-windows-server-2008.aspx