Even though nobody else has confirmed the connection between the behavior described in this report and the "Shutdown When CPU Fan Fail" BIOS option, I think it is a valid starting point, lacking anything else, also considering that the behavior itself has been confirmed by several people. I'm marking this bug as Confirmed.
** Changed in: linux-source-2.6.17 (Ubuntu) Status: Needs Info => Confirmed -- "critical temperature reached" with kernel 2.6.15-22-386 https://launchpad.net/bugs/44805 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs