I have a problem with IIS 6.0 ceasing to work for an ASP.NET application after installing Service Pack 1 for .NET 3.5.

I have 2 identical virtual dedicated servers. Installing SP1 on the first had no adverse effect. Installing it on the second caused ASP.NET pages to start returning 404 page not found.

Static .html pages working okay on both servers.

Has anybody else experienced this? Any solutions?


Some questions...

  1. Does the problem happen on every site?
  2. What happens if you create new site and add ASP.NET page?
  3. Do other scripting languages experience the same issue, e.g. asp ?

Is CustomErrors in your web.config set to On or RemoteOnly? If so, what do you get when you change it to Off?

John Sheehan

No-one did before, so I'll point to the trivial solution:
Have you already de-installed the Service Pack and re-installed it again (or the whole framework)?

Edit: @Kev:
Easy explanation: He said the update works on one machine, but not on the other. I had similar problems in the past and re-installing helped to solve some of them. And it is trivial to do.
That's my approach:
1. trivial
2. easy
3. headache

You are right, on productive systems you must be careful, but that's his decision. And because it is a virtual server, maybe it is easy for him to copy it and try as a test environment first.

John Smithers

@John - without sounding awfully negative about your answer but.... why would uninstalling/re-installing the SP or reinstalling the whole framework be classed as 'trivial' or helpful ? OP should try to understand the cause of the problem first, uninstall/reinstall can often widen the scope of the problem. If this is a production server then he should tread carefully. Trust me, I've been there. :-)

+4  A: 

This is broad problem, so let's start by asking some troubleshooting questions:

  • Based on your description, the ASP.NET runtime is not catching your request and processing the aspx files. You may need to register the pipeline with IIS again using ASPNET_REGIIS -i.
  • Have you made sure that the app_offline.htm file has been removed from the directory of the application? I have had this happen before after an update.
  • Have you setup fiddler for instance to follow the request to see what is exactly being requested?
  • Make sure ASP.NET is enabled in the IIS Administration Console under "Web Service Extensions." Make sure everything is set to allowed for your different versions of the framework.

Well, let's start with those and hopefully we can guide you to the problem.

Dale Ragan

I have not had this exact error with .NET 3.5 SP1, but have seen similar occur in the past. Typically it can be resolved by opening a command prompt, going to the appropriate .NET folder and running ASPNET_REGIIS -i. In the case of .NET 3.5 there wasn't an update to the main bits of the framework, so you'd actually go to the .NET 2.0 folder, which on my machine can be found at:


Running the ASPNET_REGIIS -i will re-register all the ASP.NET libraries with IIS, and should be the equivalent of a re-install of the framework on a given machine (as far as IIS is concerned)

Purple Ant

Just to clarify. The last (4th) point given by Dale was the problem. During the installation of SP1 the Status for ASP.NET and WebDAV became set to Prohibited under Web Service Extensions.

Why the installation of SP1 changed this setting on one server and not the other is a mystery that I wouldn't mind (but not expect) an answer to...

The second link provided by CodingTheWheel also had the answer so I'm also going to mark this as an answer.