Guys I really need your help urgently.

Our DNN Portal is down at present - we are getting the following error:

DotNetNuke.Services.Exceptions.PageLoadException: The type initializer for 'DotNetNuke.Security.Roles.RoleController' threw an exception. ---> System.TypeInitializationException: The type initializer for 'DotNetNuke.Security.Roles.RoleController' threw an exception. ---> System.TypeInitializationException: The type initializer for 'DotNetNuke.Security.Roles.RoleProvider' threw an exception. ---> System.Configuration.ConfigurationErrorsException: An error occurred creating the configuration section handler for dotnetnuke/roles: Could not load file or assembly 'DOTNETNUKE' or one of its dependencies. Access is denied. (\\Server\QLD-ProductPortal\web.config line 17) ---> System.IO.FileLoadException: Could not load file or assembly 'DOTNETNUKE' or one of its dependencies. Access is denied. File name: 'DOTNETNUKE' at System.Configuration.TypeUtil.GetTypeWithReflectionPermission(IInternalConfigHost host, String typeString, Boolean throwOnError) at System.Configuration.RuntimeConfigurationRecord.RuntimeConfigurationFactory.Init(RuntimeConfigurationRecord configRecord, FactoryRecord factoryRecord) at System.Configuration.RuntimeConfigurationRecord.RuntimeConfigurationFactory.InitWithRestrictedPermissions(RuntimeConfigurationRecord configRecord, FactoryRecord factoryRecord) at System.Configuration.RuntimeConfigurationRecord.RuntimeConfigurationFactory..ctor(RuntimeConfigurationRecord configRecord, FactoryRecord factoryRecord) at System.Configuration.RuntimeConfigurationRecord.CreateSectionFactory(FactoryRecord factoryRecord) at System.Configuration.BaseConfigurationRecord.FindAndEnsureFactoryRecord(String configKey, Boolean& isRootDeclaredHere) WRN: Assembly binding logging is turned OFF. To enable assembly bind failure logging, set the registry value [HKLM\Software\Microsoft\Fusion!EnableLog] (DWORD) to 1. Note: There is some performance penalty associated with assembly bind failure logging. To turn this feature off, remove the registry value [HKLM\Software\Microsoft\Fusion!EnableLog]. --- End of inner exception stack trace --- at System.Configuration.BaseConfigurationRecord.FindAndEnsureFactoryRecord(String configKey, Boolean& isRootDeclaredHere) at System.Configuration.BaseConfigurationRecord.GetSectionRecursive(String configKey, Boolean getLkg, Boolean checkPermission, Boolean getRuntimeObject, Boolean requestIsHere, Object& result, Object& resultRuntimeObject) at System.Configuration.BaseConfigurationRecord.GetSection(String configKey, Boolean getLkg, Boolean checkPermission) at System.Configuration.BaseConfigurationRecord.GetSection(String configKey) at System.Web.Configuration.HttpConfigurationSystem.GetApplicationSection(String sectionName) at System.Web.Configuration.WebConfigurationManager.GetWebApplicationSection(String sectionName) at DotNetNuke.Framework.Providers.ProviderConfiguration.GetProviderConfiguration(String strProvider) at DotNetNuke.Framework.Reflection.CreateObject(String ObjectProviderType, String ObjectProviderName, String ObjectNamespace, String ObjectAssemblyName, Boolean UseCache) at DotNetNuke.Framework.Reflection.CreateObject(String ObjectProviderType, Boolean UseCache) at DotNetNuke.Security.Roles.RoleProvider.CreateProvider() at DotNetNuke.Security.Roles.RoleProvider..cctor() --- End of inner exception stack trace --- at DotNetNuke.Security.Roles.RoleProvider.Instance() at DotNetNuke.Security.Roles.RoleController..cctor() --- End of inner exception stack trace --- at DotNetNuke.Security.Roles.RoleController..ctor() at DotNetNuke.Entities.Users.UserInfo.get_Roles() at DotNetNuke.Entities.Users.UserInfo.IsInRole(String role) at DotNetNuke.Security.PortalSecurity.IsInRole(String role) at DotNetNuke.Common.Globals.IsLayoutMode() at DotNetNuke.UI.Skins.Skin.Page_Init(Object sender, EventArgs e) at System.Web.UI.Control.OnInit(EventArgs e) at System.Web.UI.UserControl.OnInit(EventArgs e) at System.Web.UI.Control.InitRecursive(Control namingContainer) at System.Web.UI.Control.AddedControl(Control control, Int32 index) at System.Web.UI.ControlCollection.Add(Control child) at DotNetNuke.Framework.DefaultPage.Page_Init(Object sender, EventArgs e) at System.Web.UI.Control.OnInit(EventArgs e) at System.Web.UI.Page.OnInit(EventArgs e) at DotNetNuke.Framework.PageBase.OnInit(EventArgs e) at System.Web.UI.Control.InitRecursive(Control namingContainer) at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) --- End of inner exception

Any ideas?

We realluy don't think we have touched anything or anything has changed :-( 

if restart doesn't help, please revalidate file system permissions of the ASP.Net account.

On the site where this happened for me, it was on a hosting company.  I watched it closely for a few weeks and it has never happened again in 6 months or so.