System.NullReferenceException in .net 2.0 app

[Guest]

I am using a vendor package written in .net 2.0 C#. They say it works well,
and that I may have a configuration issue. The error I am getting is shown
below. Searching ms and google, it seems there is a hotfix, 2.0.50727.56,
affecting SYSTEM.WEB.DLL which resolves this issue.

Question: The vendor claims this works without the hotfix, can anyone
provide clues for me? How do I obtain the hotfix, if needed?

Thanks

***************

Server Error in '/Web' 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:


Line 91: throw new HttpException(404, "not found");
Line 92: }
Line 93: ASPDNSF.URLRewriter.Rewriter.Process();
Line 94: }
Line 95:

Source File: c:\Inetpub\wwwroot\smstore2\Web\App_Code\Global.asax.cs Line: 93

Stack Trace:


[NullReferenceException: Object reference not set to an instance of an
object.]
System.Web.Hosting.ISAPIWorkerRequestInProc.GetServerVariable(String
name) +1132
System.Web.Hosting.ISAPIWorkerRequest.GetServerName() +15
System.Web.HttpRequest.get_Url() +282
ASPDNSF.URLRewriter.Rewriter.Process() +56
AspDotNetStorefront.Global.Application_BeginRequest(Object sender,
EventArgs e) in c:\Inetpub\wwwroot\smstore2\Web\App_Code\Global.asax.cs:93

System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +92
System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean&
completedSynchronously) +64

Version Information: Microsoft .NET Framework Version:2.0.50727.42; ASP.NET
Version:2.0.50727.42