Unexpected and repeated log-out problem

[sf23103]

Hello,

I just purchased a new 27" iMac (fully maxed out incl. SSD)

I have used it for about an hour so far, and the only thing I've installed is firefox. Suddenly, it started going to sleep by it's self. I can wake it up and go right to the login screen, only to have it log out unexpectedly and repeatedly. I can be in firefox, safari, or with no applications open.

I turned off auto log-out, and changed the energy settings to never sleep. I repaired disk permissions. The problem persists.

I am now re-installing Mountain Lion. Any ideas?