And I can't run either SLI or Crossfire having an ATI card on a board with the nForce 4 chipset. One tip on OCing that was passed my way sometime back was to first back thing down a little and then move one or two things up gradually until things started hanging. If you bring up the cpu first the memory clock would be a little lower then the norm.
You try different combinations to see where the max is. One time the cpu first, the next time memory timings or clock settings, another seeing an fsb change. Besides the sticky there you can browse a few OC forums to see if you find some tips there for the hardwares you use.