This problem usually occurs when multiple CGI programs are executing simultaneously. Address this problem by increasing the thread limit for the server by setting the registry value MaxPoolThreads to a value that is approximately double the number of simultaneous CGI invocations you expect. If you cannot estimate the number of simultaneous CGI invocations you expect, set this value to 128. Typically, this will allow for a high user load.

Set the value for MaxPoolThreads in

   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet
      \Services\InetInfo\Parameters

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