The question says it all.
I had a QA site and PROD site on a Win 2003 server with IIS 6. I moved the sites to a new server, Win 2008 R2 with IIS 7. On the new server, I set the app pool to 2.0 for the two new sites. I tested the sites a bunch before updating the DNS to point to the new server and the sites were working fine. So I sent my client an email letting them know they could update the DNS to point to the new server.
When I got home, I started getting alerts saying the site was down. After some investigation, I found the version of .NET for the app pool had been changed to 4.0 for both sites. This brought the sites down. The client does not have access to the server. None of my other developers changed it. I didn't change it myself. It seemed to have changed by itself.
Is it possible for the .NET version of an app pool to change by itself?