Signal 11 is a bus error. I would try turning down the clock on your CPU. If this doesn't fix the problem and the memory isn't bad and the CPU isn't bad then I would go with the MotherBoard.
Well, I have only tested 3 (out of 10) systems, and they all get this error. I doubt the hardware is bad, as these are brand new systems and memtest86 doesn't report any problems, the CentOS 4.3 LiveCD boots fine, and (gasp) the pre-installed Windows XP boots fine.
I'm trying to find a way to debug this to find out the exact cause of this error. Maybe I'll start by putting the kickstart configuration file on a floppy (although I'm sure that it is being read OK from the web server)...
Alfred