Site Down: Server Error in '/' Application.The type

Ack! I was having some issues with getting an index to work, so I thought I'd try turning the indexing off and on again.

I deactivated it,  but then the site went down and gave me the error below. I checked ...\App_Data\Sitefinity\Configuration on the thought that it might have lost its database connection, but nothing's been modified for over a month.

Server Error in '/' Application.The type String cannot be constructed. You must configure the container to supply this value. 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.InvalidOperationException: The type String cannot be constructed. You must configure the container to supply this value.

Source Error:

An unhandled exception was generated during the execution of the current web request. Information regarding the origin and location of the exception can be identified using the exception stack trace below.
Stack Trace:

[InvalidOperationException: The type String cannot be constructed. You must configure the container to supply this value.]
Telerik.Microsoft.Practices.ObjectBuilder2.DynamicMethodConstructorStrategy.GuardTypeIsNonPrimitive(IBuilderContext context, SelectedConstructor selectedConstructor) +277
Telerik.Microsoft.Practices.ObjectBuilder2.DynamicMethodConstructorStrategy.PreBuildUp(IBuilderContext context) +485
Telerik.Microsoft.Practices.ObjectBuilder2.StrategyChain.ExecuteBuildUp(IBuilderContext context) +434
Telerik.Microsoft.Practices.ObjectBuilder2.DynamicMethodBuildPlanCreatorPolicy.CreatePlan(IBuilderContext context, NamedTypeBuildKey buildKey) +400
Telerik.Microsoft.Practices.ObjectBuilder2.BuildPlanStrategy.PreBuildUp(IBuilderContext context) +222
Telerik.Microsoft.Practices.ObjectBuilder2.StrategyChain.ExecuteBuildUp(IBuilderContext context) +434
Telerik.Microsoft.Practices.ObjectBuilder2.BuilderContext.NewBuildUp(NamedTypeBuildKey newBuildKey) +318
BuildUp_Telerik.Sitefinity.Modules.Pages.PageManager(IBuilderContext ) +220
Telerik.Microsoft.Practices.ObjectBuilder2.BuildPlanStrategy.PreBuildUp(IBuilderContext context) +304
Telerik.Microsoft.Practices.ObjectBuilder2.StrategyChain.ExecuteBuildUp(IBuilderContext context) +434
Telerik.Microsoft.Practices.Unity.UnityContainer.DoBuildUp(Type t, Object existing, String name, IEnumerable`1 resolverOverrides) +440

[ResolutionFailedException: Resolution of the dependency failed, type = "Telerik.Sitefinity.Modules.Pages.PageManager", name = "OPENACCESSDATAPROVIDER".
Exception occurred while: while resolving.
Exception is: InvalidOperationException - The type String cannot be constructed. You must configure the container to supply this value.
-----------------------------------------------
At the time of the exception, the container was:

Resolving Telerik.Sitefinity.Modules.Pages.PageManager,OPENACCESSDATAPROVIDER
Resolving parameter "providerName" of constructor Telerik.Sitefinity.Modules.Pages.PageManager(System.String providerName, System.String transactionName)
Resolving System.String,(none)
]
Telerik.Microsoft.Practices.Unity.UnityContainer.DoBuildUp(Type t, Object existing, String name, IEnumerable`1 resolverOverrides) +546
Telerik.Microsoft.Practices.Unity.UnityContainer.DoBuildUp(Type t, String name, IEnumerable`1 resolverOverrides) +20
Telerik.Microsoft.Practices.Unity.UnityContainerExtensions.Resolve(IUnityContainer container, String name, ResolverOverride[] overrides) +91
Telerik.Sitefinity.Data.ManagerBase`1.GetManager(String providerName, String transactionName) +660
Telerik.Sitefinity.Web.SiteMapBase.GetPageManager() +56
Telerik.Sitefinity.Web.SiteMapBase.GetRootNodeCore(Boolean ifAccessible) +362
Telerik.Sitefinity.Web.SiteMapBase.FindSiteMapNode(String rawUrl, Boolean ifAccessible, Boolean unresolveUrl, Boolean& isAdditionalUrl, String[]& urlParameters) +859
Telerik.Sitefinity.Web.SitefinityRoute.FindSiteMapNode(String& virtualPath, SiteMapBase siteMapProvider, Boolean& isAdditional, String[]& pars, Boolean skipSubSiteCheck) +512
Telerik.Sitefinity.Web.SitefinityRoute.GetRouteData(HttpContextBase httpContext) +247
System.Web.Routing.RouteCollection.GetRouteData(HttpContextBase httpContext) +251
System.Web.Routing.UrlRoutingModule.PostResolveRequestCache(HttpContextBase context) +79
System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +80
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +165

Version Information: Microsoft .NET Framework Version:4.0.30319; ASP.NET Version:4.0.30319.18408

...and now it's back up again. Go figure.

Hi Ernest,
 

If the project has been upgraded make sure the upgrade has been performed according to the documentation, please, go to Administration-Modules and see what the status of the Search and Indexes module is. Try installing/activating the module. 

Additionally make sure application pool's identity has read/write permissions to the App_Data folder of the project and that is owner of the database and its schema.