Hi all,

We have a couple of Umbraco websites where the application pools are spontaneously shutting down.We believe the problem to be related to a memory leak within the sites but we are having issues identify where exactly this is happening.

The event viewer on the server always returns "A process serving application pool 'xxx' exceeded time limits during shut down. The process id was 'nnnnn'.".

Here are things we have already tried:

• Setting up the debug diagnostic tool to catch any crash or hangs on application pools.
• Running ANTS Memory Profiler to help identify where any possible memory issues may arise.
• Utilising the built-in Umbraco debug trace to determine if the issue is within macros.

The debug diagnostic tool always has the following two error messages:

w3wp__PID__9904__Date__04_01_2011__Time_02_22_11PM__207__Second_Chance_Exception_E0434F4D.dmp 
the assembly instruction at kernel32!RaiseException+53 in 
C:\WINDOWS\system32\kernel32.dll from Microsoft Corporation has 
caused a CLR Exception of type (System.NullReferenceException) on thread 18

This exception originated from 
mscorwks!RaiseTheExceptionInternalOnly+2a8. 

w3wp__PID__4496__Date__04_04_2011__Time_10_01_52AM__703__Second_Chance_Exception_E0434F4D.dmp 
the assembly instruction at kernel32!RaiseException+53 in 
C:\WINDOWS\system32\kernel32.dll from Microsoft Corporation has 
caused a CLR Exception of type (System.IO.IOException) on thread 15

This exception originated 
from mscorwks!RaiseTheExceptionInternalOnly+2a8. 

Each website has its own individual application pool. We are running on Windows Server 2003, MSSQL Server 2005 and IIS6.

Has anyone experienced similar issues before or having any ideas what might be causing this?

Many thanks,
Dave