This may be well off the mark, but it might be worth considering:
I installed F3 on an old Celeron 700 Box with 160meg. More often than not it would either hang, or reboot just after the Grub screen. No matter what I did made any difference. Then I put another 256Meg of memory and, from memory, it hasn't crashed at boot at all. You have even less memory. Maybe drop some more in just to test it.