Server Error in '/' Application.

Object reference not set to an instance of an object.

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.NullReferenceException: Object reference not set to an instance of an object.

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:

[NullReferenceException: Object reference not set to an instance of an object.]

DNA.UI.ClientScriptManager.RegisterScriptsOnPagePreRenderComplete(Object sender, EventArgs e) +210

System.EventHandler.Invoke(Object sender, EventArgs e) +0

System.Web.UI.Page.OnPreRenderComplete(EventArgs e) +107

System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +4885

Version Information: Microsoft .NET Framework Version:2.0.50727.4200; ASP.NET Version:2.0.50727.4016

Would be delighted if anyone could give an answer to what's wrong.