I have "Fatal trap 18: integer divide fault while in kernel mode" error than install FreeNAS 0.7 or 0.7RC1. FreeNAS 0.69.2 works fine on the same system.
I tried second almost the same system (with newer version of the same system board based on Intel P35 chipset) with different CPU installed (Pentium 4 Quad), and FreeNAS 0.7 & 0.7RC1 installs fine on that system. Thus, I hope that this is a CPU-related problem.
The issued system CPU ID is 0F65h (Processor Family F, Model 6, Steping 5), or Pentium 4 641 - 3.2 GHz, "Cedar Mill" Stepping D0, SL9KF. It has one physical CPU Core and 2 logical ones (HT enabled).
Probably, the problem is related to wrong settiing of cpu_cores or cpu_logical to 0 by CPU identification routine (FreeBSD issue r191648), http://lists.freebsd.org/pipermail/freebsd-current/2009-April/006388.html.
Sorry, I have no logs due to no writable filesystems mounted during the fault.