Sounds like bad luck to me...
My XP1600+ is running 146.8FSB rock solid, using 2x Crucial DDRs at full speed, and stock voltages no less.. What is your
PSU?... if you have MBM, check your voltages, to make sure you have enough juice to feed the new baby. Definitely slow down your timings on the
RAM to see if the
CPU responds to the FSBs.