title: System.Security.SecurityException thrown by ASP.NET application
body: <p>Trying to get an ASP application deployed; it worked for a while but then started coming up with errors whenever the page is accessed:</p>
  
  <blockquote>
    <h2>Server Error in '/AppNameHere' Application.</h2>
    
    <p>Security Exception Description: The application attempted to perform
    an operation not allowed by the security policy. To grant this
    application the required permission please contact your system
    administrator or change the application's trust level in the
    configuration file.</p>
    
    <p>Exception Details: System.Security.SecurityException: Request for the
    permission of type 'System.Web.AspNetHostingPermission, System,
    Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089'
    failed.</p>
  </blockquote>
  
  <p>An IISreset didn't change anything, but rebooting the entire system got it to work for a few hours before the problem came back. The <code>.config</code> for the application is set to full trust.  </p>
  
  <p>What could be causing this, and how can it be fixed?  (Or, if more information is needed, where do I go looking to find it)</p>