I had many programs opened and was typing a message in my web browser and suddenly a window asking me something popped up. I think I was in the middle of typing the word "for" but whatever button I hit seemed to be the confirmation to shutdown the computer. Is there a way to find which program caused this and prevent it in the future? I have a hunch it was JDownloaders fault.
I'm using Windows 7.
You could try examining the logs around the time of shut down and see if you can spot anything.
To figure out when your PC was last shut down, you can simply open up Event Viewer, head into the Windows Logs -> System log, and then filter by Event ID 6006, which indicates that the event log service was shut down—one of the last things that happens before a shutdown.
You might be able to see what did it, though I'm not sure if such things are logged.
As an aside it is sometimes possible to abort a shutdown with (from the commandline)
shutdown -a
(but you have to be quick)
You may (depending on your distro) be able to see some form of log in /var/log/{messages,system} or, if as you suspect it was an app of yours running in the background that did it, in your ~/.xsession-errors.
But as a generic rule such events don't get logged.
