If you got an error, your memory is unstable. Your system is not suitable for mission critical work. Try loosening some memory timings if they were tightened, try going back to stock clocks if the memory was overclocked, try improving air flow in your case.
If none of that works, then either your memory is defective, or your motherboard memory slots could be broken. If you have an Athlon 64, it is possible the on die memory controller is broken.