I was having a hell of a time tonight with my IIS on my development laptop. I don’t remember doing anything to change the IIS settings. I don’t use IIS that much on my dev machine. Usually Cassini is enough for testing my development efforts but tonight I needed to replicate a problem that seems to stem from x86 v x64 mismatch, so I went to create an IIS site pointed to my dev folder.

When I did, I got a “503.1 Service Unavailable Error”.

First thing I did is go over all my setting to make sure I didn’t screw something up when I set up the site. It was pointing to the right place, and the app pool settings seemed to be alright. However, when I got the 503.1 error and went back to my app pool list, I saw that the app pool I was using was stopped again. I must’ve started and ran it a dozen times to verify that I wasn’t seeing things. After having a colleague look at it and not finding an answer, I started poking around Google. I cam across a post from Phil Haack about the same error. His fix was not mine, however. When I ran his command on the CLI, I didn’t see the reserved routes for HTTP.SYS there.

Finally, I looked in the event viewer (where I should have looked as soon as I saw that my app pool was stopping) and saw an error in there. For the IIS-W3SVC-WP Source I saw:

The worker process for application pool 'DefaultAppPool' encountered an error 'Cannot read configuration file due to insufficient permissions

' trying to read configuration data from file '\\?\C:\Windows\Microsoft.NET\Framework64\v4.0.30319\CONFIG\machine.config', line number '0'. The data field contains the error code.

So I went to that path and saw a little lock on the file icon. I opened up the security tab for file properties and saw that I was missing the IIS_IUSRS group. On a machine that was working correctly, I verified that it indeed had the IIS_IUSRS group set to Read and Read & Execute allowed. So I set mine up the same and voila!

Hopefully this helps somebody else, too.