I recently ran into an issue where after deploying a web application to a web server, I got the Yellow Screen of Death. I opened the site on the server and it turns out that the ASP.NET State Service was not running. Sigh. Everything was working before so I figured I'd just need to start the service. Except, the service was gone!
The server had recently been taken down for a short period of time so that a snapshot could be taken of it. Is it possible that caused the problem? I'm not really sure.
I ran across this blog post that suggested just re-registering ASP.NET with IIS would fix the problem. This server isn't in production yet, so I was fine trying the method. Luckily, it worked and the service was once again installed.
To re-register ASP.NET, open a command prompt as administrator, change directory to the version of .NET you want to register, and run the following commands: