why My app crashes "Access to Bad" when I am pushing controllers i UINavigationController

Hi all why My app 开发者_运维知识库crashes "Access to Bad" when I am pushing controllers in UINavigationController I am also using some static variables to store data. Please help I am using UINavigationController , and I push many controllers in it ,but some time my app crashed saying "Access to the bad Request" ,Is this happening due to static variables ?

this happens because you accessing some released object