We recently converted from IIS 6 to IIS 7.5 under Windows 7 (development) and Windows Server 2008 R2 (production). We are running 6 websites in Classic mode and allowing 32-bit applications.
All the sites run fine until I change anything in a website folder. For my latest test, I recycle the application pool, load the default page, and touch "web.config". Every request following this immediately returns this error.
There is nothing in any of the event viewer logs. There is nothing in the server log. The website log shows a 500 error returned for every request. The Failed Request Log trace shows Internal Server Error in MODULE_SET_RESPONSE_ERROR_STATUS following AspNetGetAppDomainLeave in C:\Windows\Microsoft.NET\Framework\v2.0.50727\aspnet_isapi.dll.
Task Manager shows the worker process w3wp.exe (app pool only allows 1) is still running.
If I recycle the app pool or kill the worker process, the site works again--until I make any other change.
I have been searching the internet for days and have found many issues of this Check Engine error but nothing with the symptoms I describe.
Does anyone have any idea how I might go about trying to diagnose this?