Updating 4.08.04 to 4.09.00 update workded prefectly on our local development server but filed when trying it on our ISP vertual server.  Got the following:

Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.IO.FileLoadException: Could not load file or assembly 'CountryListBox' or one of its dependencies. Access is denied.

Stack Trace:

[FileLoadException: Could not load file or assembly 'CountryListBox' or one of its dependencies. Access is denied.]
   System.Reflection.Assembly.nLoad(AssemblyName fileName, String codeBase, Evidence assemblySecurity, Assembly locationHint, StackCrawlMark& stackMark, Boolean throwOnFileNotFound, Boolean forIntrospection) +0
   System.Reflection.Assembly.InternalLoad(AssemblyName assemblyRef, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection) +211
   System.Reflection.Assembly.InternalLoad(String assemblyString, Evidence assemblySecurity, StackCrawlMark& stackMark, Boolean forIntrospection) +141
   System.Reflection.Assembly.Load(String assemblyString) +25
   System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective) +32

[ConfigurationErrorsException: Could not load file or assembly 'CountryListBox' or one of its dependencies. Access is denied.]
   System.Web.Configuration.CompilationSection.LoadAssemblyHelper(String assemblyName, Boolean starDirective) +596
   System.Web.Configuration.CompilationSection.LoadAllAssembliesFromAppDomainBinDirectory() +3479033
   System.Web.Configuration.CompilationSection.LoadAssembly(AssemblyInfo ai) +46
   System.Web.Compilation.BuildManager.GetReferencedAssemblies(CompilationSection compConfig) +177
   System.Web.Compilation.BuildProvidersCompiler..ctor(VirtualPath configPath, Boolean supportLocalization, String outputAssemblyName) +180
   System.Web.Compilation.CodeDirectoryCompiler.GetCodeDirectoryAssembly(VirtualPath virtualDir, CodeDirectoryType dirType, String assemblyName, StringSet excludedSubdirectories, Boolean isDirectoryAllowed) +347
   System.Web.Compilation.BuildManager.CompileCodeDirectory(VirtualPath virtualDir, CodeDirectoryType dirType, String assemblyName, StringSet excludedSubdirectories) +125
   System.Web.Compilation.BuildManager.EnsureTopLevelFilesCompiled() +378

[HttpException (0x80004005): Could not load file or assembly 'CountryListBox' or one of its dependencies. Access is denied.]
   System.Web.Compilation.BuildManager.ReportTopLevelCompilationException() +57
   System.Web.Compilation.BuildManager.EnsureTopLevelFilesCompiled() +612
   System.Web.Hosting.HostingEnvironment.Initialize(ApplicationManager appManager, IApplicationHost appHost, IConfigMapPathFactory configMapPathFactory, HostingEnvironmentParameters hostingParameters) +456

[HttpException (0x80004005): Could not load file or assembly 'CountryListBox' or one of its dependencies. Access is denied.]
   System.Web.HttpRuntime.FirstRequestInit(HttpContext context) +3426839
   System.Web.HttpRuntime.EnsureFirstRequestInit(HttpContext context) +88
   System.Web.HttpRuntime.ProcessRequestInternal(HttpWorkerRequest wr) +149

Has anyone seen this and how do I recover.

It looks like you need to reapply file permissions to the site, specifically CountryListBox.dll in your bin folder, but probably others as well.

If you have remote desktop access to the machine, you'll right click on the website folder, select Properties, switch to the Security tab, then make sure that the NETWORK SERVICE use has modify permissions on the site.  Once that is set, select the Advanced button, and check the "Replace permission entries on all child objects..." option, to make sure that permission applies to all of the files in the site.

Hope that helps!