I think you can a take deep look at these articles which will help you to go down the stack on limits, how they are set , how problem starts cropping up etc.
http://blogs.technet.com/b/markrussinovich/archive/2009/07/08/3261309.aspx
http://blogs.technet.com/b/markrussinovich/archive/2008/07/21/3092070.aspx
Good luck!
Tnx!