Hi,
from a lot of days i get always this error.

Server Error in '/' Application.
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Value cannot be null.
Parameter name: type
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.ArgumentNullException: Value cannot be null.
Parameter name: type

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:

[ArgumentNullException: Value cannot be null.
Parameter name: type]
   System.Activator.CreateInstance(Type type, Boolean nonPublic) +2843451
   DotNetNuke.Framework.Reflection.CreateObject(String ObjectProviderType, String ObjectProviderName, String ObjectNamespace, String ObjectAssemblyName, Boolean UseCache) +582
   DotNetNuke.Data.DataProvider.CreateProvider() +46
   DotNetNuke.Data.DataProvider..cctor() +13

[TypeInitializationException: The type initializer for 'DotNetNuke.Data.DataProvider' threw an exception.]
   DotNetNuke.Common.Globals.GetUpgradeStatus() +67
   DotNetNuke.Common.Initialize.CheckVersion(HttpApplication app) +147
   DotNetNuke.Common.Initialize.InitializeApp(HttpApplication app) +413
   DotNetNuke.Common.Initialize.Init(HttpApplication app) +125
   DotNetNuke.HttpModules.RequestFilter.RequestFilterModule.FilterRequest(Object sender, EventArgs e) +177
   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +92
   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +64

--------------------------------------------------------------------------------
Version Information: Microsoft .NET Framework Version:2.0.50727.1433; ASP.NET Version:2.0.50727.1433

What can i do ?

I Use lst 4.8.4. Version on a Windows 2003 Server with last update and SP and SQL Express with last SP

Thank in advance

Thanks for the reply.
before this error (that i get from web pages) the site freezes due to a .NET Runtime error

.NET Runtime version 2.0.50727.1433 - Errore irreversibile del motore di esecuzione (79FFEE24) (80131506)

that have this .NET Runtime 2.0 Error Reporting

Faulting application w3wp.exe, version 6.0.3790.3959, stamp 45d6968e, faulting module unknown, version 0.0.0.0, stamp 00000000, debug? 0, fault address 0x70c02075.

so i must kill the w3wp.exe process and reload the page again.

thanks again

I apologize for the missing translation, anyway 
"Errore irreversibile del motore di esecuzione"
means
"Irreversible error on execution engine":

No i dont' have any 3rd party provider or HTTP modules.

Thanks again