This might not help, but I wanted to comment that I spent hours on this same error and found the solution to my problem. It turned out to be something that nobody else ever documented, so I'm trying to spread the word for Google.
It turned out that my root web was working fine, but my subwebs were not working fine and I got this error for the subweb. The subweb was an individually configured ASP.NET application. I figured that this wasn't important because the root web was just a flat HTML file, but it mattered.
What happened in my case was that a few days ago I had relocated the root web, then updated IIS to point to the new directory. All of the subweb applications, however, were treated by IIS as virtual directories, each with its own physical directory mapping. So each had the stale path.
More specifically, I moved "C:\web\www.mysite.com" to "C:\web\mysite.com", updated IIS for MySite to point to \web\mysite.com, and left it as such. The applications under mysite.com were each pointing to C:\web\www.mysite.com\[application].
I had to update each subweb application's Basic Settings to point to the revised path, and the 500.19 error went away.
Hope this helps others like it would've helped me.
Jon