I know after reading about WM_QUERYENDSESSION that windows typically sends this message to all running applications when a user is either logging off, restarting, or shutting a PC down. I have an application with a handler for when this event is received, so I can see that the WM_QUERYENDSESSION message is coming in, but I don't know what is causing it. The user claims that the application "stops working" suddenly and freezes up, and I assume that they weren't logging off or restarting or shutting down the PC. Is there any other instance in which the WM_QUERYENDSESSION could be sent out to applications or is there a something I can look for in determining what caused it?