title: IIS errors since upgrading to dot net 4
body: <p>Back in October we upgraded one of our sites (on IIS 6) from .net 3.5 to .net 4.0. Since then we have been getting the following warning and error pretty much everyday:</p>
  
  <p>Warning:</p>
  
  <blockquote>
    <p>ISAPI
    'c:\windows\microsoft.net\framework\v4.0.30319\aspnet_isapi.dll'
    reported itself as unhealthy for the
    following reason: 'Deadlock detected'.</p>
  </blockquote>
  
  <p>Error:</p>
  
  <blockquote>
    <p>It is not possible to run two
    different versions of ASP.NET in the
    same IIS process. Please use the IIS
    Administration Tool to reconfigure
    your server to run the application in
    a separate process.</p>
  </blockquote>
  
  <p>We have checked all applications and ensured that they are running on the correct versions of ASP.NET and also in their own separate app pools. </p>
  
  <p>We have looked at the IIS logs at the time the errors are recorded but this doesn't give any clues as to the issue. Is there a tool available that could give us more information as as to which application is causing the errors and what was happening at the time?</p>