Mac Pro logs out due to inactivity?

Hi all,

Everytime I leave my Mac Pro for a while (30mins-ish seems to be long enough) and come back, it has attempted to log out, so half my programs are closed, and Safari usually has stopped it because of having multiple tabs open (so it shows the message "Safari stopped the logout").

I turned the screensaver off to see if that caused the problem, but that hasn't helped.

I am pretty sure I haven't set it to do this, but has anyone any thoughts? It has been doing it for a few days now.

Cheers,
R

Thanks, I must have accidently checked that when I went to turn on secure virtual memory.