title: Cause of event id 1309 asp.net 4.0 unhandled exception in asp.net
body: <p>I am working on website, yesterday i faced a problem i.e server got down. i have checked the event log files then i came to know that it was due to "event id 1309 asp.net 4.0 unhandled exception" error. i just restore the back up of the website and restart the website it got worked. </p>
  
  <p>Now my concern is why i got this error: is the criteria i had followed is actual way to recover from this error. i am asking this because might be we will not have latest code back up in future then what will we do? so i am asking to experts </p>
  
  <ol>
  <li>why this errors occurred, what is exact caused for this.? </li>
  <li>Best way to overcome this.</li>
  </ol>
  
  <p>I have read the<a href="http://support.microsoft.com/kb/941386" rel="nofollow">This link</a> and came to know this is due to
  <strong>This problem occurs because the public headers properties of the Request.Headers property and of the Response.Headers property become non-serializable after you install the MS07-040 security update</strong></p>
  
  <p>But i have not used "Request.Headers".. please guide me.</p>