Windows XP gave me a crazy error message. My fingers automatically pressed the print screen button and here is the screenshot (Click on the thumbnail to open the full version) .
This message appeared after a brief period of inactivity and once I pressed ok my system back to action. 
Well, I guess someone at Microsoft have forgotten to check a variable is null or not 
. A simple Google search revealed that I am not the first one to get an error in an error message