I've had this happen when I have a crash and I try to save my work with ctrl-S to save. My document is ruined. Once I had it crash during a render and when I came back after reboot, that document went into permanent render mode. It would just sit and render over and over. I couldn't stop it. It always loaded with the render screen already running. So frustrating. I've found no way to fix this and ended up just recreating the whole scene from scratch. What a pain. Melanie