From: GlobalArchitect on
I have an ASP.NET website that has been running fine for about 16 months
until I start using the .NET 4.0 framework and I started building the
codebase in Visual Studio 2010.

Now IIS crashes all of the time and it appears as if the site is being
spontaneously deregistered from the v4.0 Integrated Application Pool. The
only way I can fix this issue is to turn off IIS, try browsing to the page
(thus getting a website not found) and then turning IIS back on.

I did try recycling the application pool but that led to a series of 503
errors that were only resolved by rebooting the server and repeating the
steps above.

At first I thought this only occurred when I posted new code but now it is
happening even when the code is not touched.

I am running IIS 7 on a Windows 2008 server using the ASP.NET v4.0
Application Pool Integrated (not the classic). When the site goes down, it
no longer appears to be registered to the application pool but when I perform
the steps above, it once again appears in the Application Pool and the site
works once again.

I base this on the fact that, when the site is down, the number of
applications registered to the v4.0 pool is 0. After repeating the steps
above, the site comes back online and the number of applications is 1.

Please help!
From: GlobalArchitect on
I figured out this issue in case others get stuck. First tryig looking into
unlocking your applicationHost.config file as that appears to be a common

In my case, however, I am using the URLRewrite feature which is an extension
of IIS. I was using the 1.1 version and that version is not compatible with
the 4.0 framework. Once I upgraded to the 2.0 version my problem was