I'm running an ASUS MOBO with an Intel i7 @ 3.5 GHz, 16 GB RAM, Win 7 64 bit, and LR4.2
Not one crash or misstep. Occasionally when I use multiple Adjustment Brushes, it slows down, but I think I've overloaded the CPU on those occasions.
A longshot: Several years ago on a music forum for EMU products, there were consistent crashes with some MOBOs, while some MOBOs were rock solid. I was a fortunate one.