I'm trying to install dnn 5.0 but the same error occurs each time. This happens when i click the next button on the first page of the installation. I'm using the same webserver as my dnn4 installations with asp.net 2.0 and the same dbserver with just a new db :

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.ArgumentException: Invalid JSON primitive: . at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializePrimitiveObject() at System.Web.Script.Serialization.JavaScriptObjectDeserializer.DeserializeInternal(Int32 depth) at System.Web.Script.Serialization.JavaScriptObjectDeserializer.BasicDeserialize(String input, Int32 depthLimit, JavaScriptSerializer serializer) at System.Web.Script.Serialization.JavaScriptSerializer.Deserialize(JavaScriptSerializer serializer, String input, Type type, Int32 depthLimit) at System.Web.Script.Serialization.JavaScriptSerializer.Deserialize[T](String input) --- End of inner exception stack trace --- at System.RuntimeMethodHandle._InvokeMethodFast(Object target, Object[] arguments, SignatureStruct& sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner) at System.RuntimeMethodHandle.InvokeMethodFast(Object target, Object[] arguments, Signature sig, MethodAttributes methodAttributes, RuntimeTypeHandle typeOwner) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture, Boolean skipVisibilityChecks) at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture) at DotNetNuke.UI.Utilities.Reflection.InvokeGenericMethod[T](Type Type, String MethodName, Object Target, Object[] Args) at DotNetNuke.UI.Utilities.MSAJAX.Deserialize[T](String Data) at DotNetNuke.UI.Utilities.ClientAPI.GetClientVariableList(Page objPage) at DotNetNuke.UI.Utilities.ClientAPI.RegisterClientVariable(Page objPage, String strVar, String strValue, Boolean blnOverwrite) at DotNetNuke.UI.Utilities.ClientAPI.RegisterClientReference(Page objPage, ClientNamespaceReferences eRef) at DotNetNuke.UI.Utilities.ClientAPI.RegisterClientReference(Page objPage, ClientNamespaceReferences eRef) at DotNetNuke.UI.Utilities.ClientAPI.GetCallbackEventReference(Control objControl, String strArgument, String strClientCallBack, String strContext, String srtClientErrorCallBack, String strClientStatusCallBack, String strPostChildrenOfId, CallBackTypeCode eCallbackType) at DotNetNuke.UI.Utilities.ClientAPI.GetCallbackEventReference(Control objControl, String strArgument, String strClientCallBack, String strContext, String srtClientErrorCallBack) at DotNetNuke.Services.Install.InstallWizard.Page_Load(Object sender, EventArgs e) at System.Web.UI.Control.OnLoad(EventArgs e) at System.Web.UI.Control.LoadRecursive() at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)

I've already tried although I think this is not the reason for the error.

I will try to reinstall the Ajax components. But it is strange because of all the dnn4 websites on the same server. These websites are using ajax for similar modules, so this means Ajax is well installed?